Well, not any, but I'm finding my players getting way too much use out of this.
If they start a detect magic and concentrate for a couple rounds, they can effectively Find Traps, and See Invisibility. These are both second-level spells. They recently encountered an open field they had to negotiate with a minefield of magical traps randomly scattered around. The DC for finding the traps was relatively high, so even if they had a rogue, he might not have detected them. A couple rounds of concentration with a 0-level spell, of which they have infinite uses, and the high-level challenge is not a challenge at all.
The rogue searches a door for traps, and misses the roll. A player casts Detect Magic, and in a couple rounds, tells the rogue, "You missed it. Check it again." So much for skill. He can even tell the school of magic and logically deduce a good spell to prep the rogue with in the event he fails the disarm.
Walking into a room later on, there was a lurking invisible creature maneuvering into position. Since they had Detect Magic active already, and all the players who had it were maintaining it, they not only know it's there, they pinpoint its location, the second they walk into the room. It's a standard action to maintain concentration, but they designate one player to point out where it went, and the invisible enemy's a piñata.
They find a pool of murky water. Anything in it? Detect magic. That character with all the ranks in Search feels pretty redundant about now.
The fact that it's usable at will means there is no consequence to keeping it on constantly, only dropping it when you need your standard action to fight. Which makes Arcane Sight, a 3rd level spell, nearly totally worthless.
Those are just the uses I've seen. I suppose one could argue this is a clever use of a spell to solve a problem. I think it's an exploit, and a pretty damaging one, at that. It negates a few of the trademark tricks of some monsters, and makes it pointless to put magical traps (or at least to bother concealing them) in a dungeon.
Is anyone else finding this to be a problem?
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It's not been much of a problem in the games I play in, because none of us would have fun being a glorified metal detector than finds magic instead of metal. If this is the group's normal operation, and it's not as fun to set up magical traps and invisible creatures anymore, I offer the following option.
Magic Aura and Nondetection spells will stop Detect Magic. A mass illusion spell on the room will hide the invisible creature, and not all hard to find traps have to be magical. Same thing with invisible creatures.
Take a bit from Detect Evil and apply it to Detect Magic. If the magical aura is far more powerful than the 'Magic Detectot', he's stunned for 1 round.
If they start a detect magic and concentrate for a couple rounds, they can effectively Find Traps, and See Invisibility. These are both second-level spells. They recently encountered an open field they had to negotiate with a minefield of magical traps randomly scattered around. The DC for finding the traps was relatively high, so even if they had a rogue, he might not have detected them. A couple rounds of concentration with a 0-level spell, of which they have infinite uses, and the high-level challenge is not a challenge at all.
Let the traps be obvious then instead. Make the problem not detecting the trap but instead just finding a way to bypass it. Mechanical traps will still give the rogue something to do as well.
Walking into a room later on, there was a lurking invisible creature maneuvering into position. Since they had Detect Magic active already, and all the players who had it were maintaining it, they not only know it's there, they pinpoint its location, the second they walk into the room. It's a standard action to maintain concentration, but they designate one player to point out where it went, and the invisible enemy's a piñata.
There have been threads about this elsewhere on the boards. I believe the consensus is that detect magic can't do more than tell you it's there. Also, this requires several rounds to do. I'd hope the invisible creature would have attacked by then, perhaps aiming at the guy standing around maintaining concentration since he's an obvious threat that isn't being productive.
They find a pool of murky water. Anything in it? Detect magic. That character with all the ranks in Search feels pretty redundant about now.
Then the party can leave behind all those nice gems you put in the water that weren't magical but instead hidden under a rock. And the jewelry. Vases. Well-crafted but nonmagical weapons and armor made of precious metals.
The fact that it's usable at will means there is no consequence to keeping it on constantly, only dropping it when you need your standard action to fight. Which makes Arcane Sight, a 3rd level spell, nearly totally worthless.
Consequence: yes, you can have it continually active. But since you need those standard actions to get anything beyond the basic 'there's magic here', your party isn't going to move very fast as the caster only may take a move action each round. That gives the bad guys time to prep for their arrival or even leave the area. Buildings can be set on fire, hostages slain, the possibilities are endless.
Those are just the uses I've seen. I suppose one could argue this is a clever use of a spell to solve a problem. I think it's an exploit, and a pretty damaging one, at that. It negates a few of the trademark tricks of some monsters, and makes it pointless to put magical traps (or at least to bother...
Again, unless the whole party waits for several rounds while your caster finds out all the information, there's really not much to gain here at higher levels. Enchant an entire building with abjuration magic, like guards and wards or forbiddance. The whole place will radiate magic to him. Then he'll have to spend time to notice anything that isn't whitewashed out in the background as well as find himself with a headache from staring at a glowing world constantly. And at high levels, much of the world really IS magical.
Bella Sara Charter Superscriber
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I've never been a fan of having detect magic used to find traps. I've come to terms with it being used to detect invisibility, and am generally okay with that given how long it takes to perform.
For traps, as mentioned above, I assume that part of making a magic trap is rendering it invisible to detect magic. Do you need nondetection? Is there a version of Nystul's (Non)-Magical Aura in Pathfinder?
We always assumed that each time you focus on a different area or subject, the round timer starts over. So if your group walks into a room and detects magic in the room (and there is an invisible enemy in the room), they know there is a magic aura in the room in round 1 but that is all. Then it's the invisible enemy's turn and combat is initiated as normal.
Also bear in mind that stronger emanations can conceal weaker ones.
It's a useful tool to be sure, but it shouldn't be a game breaker.
Initially, yes. Then I realized that, in the world of Golarion, any trapmaker worth his or her salt will have a Nondetection cast onto magical traps or secret doors or other things they want kept hidden.
Or surround the trap with lead foil.
Or put the trap around a corner of a 3 foot thick wall of stone.
and my favorite.
Use detect magic as the trigger for your magic traps, when the trap detects magic it sets off an AoE spell. The mage walking forward into the range of the detect magic sets off the trap as soon as they detect it.
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I've never been a fan of having detect magic used to find traps. I've come to terms with it being used to detect invisibility, and am generally okay with that given how long it takes to perform.
For traps, as mentioned above, I assume that part of making a magic trap is rendering it invisible to detect magic. Do you need nondetection? Is there a version of Nystul's (Non)-Magical Aura in Pathfinder?
Sorry, I always get those two mixed up. Yes, Magic Aura is what I meant. 1st level spell, lasts for 1 day/level. Or just make it permanent.
Good stuff
To add to that, any time a player with a magic item walks in front of the person detecting magic, it will set off their magic sense. Then they will have to spend 2-3 rounds figuring out that the magic they detected is the barbarian's greatsword. This means that after level 3 or 4, the caster will have to be in the front of the group for this trick to work. That opens them up to getting clobbered by all sorts of mundane traps, and you really don't want the mage in front if the party gets ambushed.
There have been threads about this elsewhere on the boards.
I did look for one, but, I admit, not very hard.
I believe the consensus is that detect magic can't do more than tell you it's there. Also, this requires several rounds to do.
Yeah, a close reading of the spell told me that the caster must spend the time studying the area or object, so they can't walk around with the round-3 effect (exact location) to be ready the instant they walk in the room. But in the one case it mattered, the invisible enemy took a couple rounds stealthily moving into position for a melee attack, at which time he was lit up.
I'd hope the invisible creature would have attacked by then, perhaps aiming at the guy standing around maintaining concentration since he's an obvious threat that isn't being productive.
Yeah, but a few shouts of "IT'S RIGHT HERE! IT'S RIGHT HERE! GET IT OFF ME! AAHHH!!" will do wonders for pinpointing a square to attack.
I agree with your suggestions, but I still think the spell is a little too prone to exploit.
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Bella Sara Charter Superscriber
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Good stuffTo add to that, any time a player with a magic item walks in front of the person detecting magic, it will set off their magic sense. Then they will have to spend 2-3 rounds figuring out that the magic they detected is the barbarian's greatsword. This means that after level 3 or 4, the caster will have to be in the front of the group for this trick to work. That opens them up to getting clobbered by all sorts of mundane traps, and you really don't want the mage in front if the party gets ambushed.
Oooh. I like this. And the suggestion of having a trap be triggered by the detect magic.
Oooh. I like this. And the suggestion of having a trap be triggered by the detect magic.
Yeah, those are good.
Two words for the Detect Magic trap: Chain Lightning.
If the entire party is okay with using Detecting Magic to find everything, they can use to find cure potions at the market.
A lightning bolt in a 5 foot wide hallway works as well.
There have been threads about this elsewhere on the boards.I did look for one, but, I admit, not very hard.
Pretty much everything we are going to think of here was probably already said there.
DM: X concentrates and begins to pin down the source of the magical emanation...it's riight...BEHIND YOU! *monster attacks*
Detect magic is a cone, it doesn't detect things that are "behind" you.
Everyone has already offered stellar advice here, so I don't have a lot more to add, but my rogue player asked for a magic item that activated Detect Magic at will... and I gave it to him. Why?
At the risk of being repetitive...
He still has to disarm the magical trap. And some traps auto-reset. Not all traps are magical--some of my favorite traps are mechanical traps.
As noted, it takes a few moments for distinct auras to form. If they're in a hurry, all they know is "magic is here" which may not be helpful.
Knowing an invisible character is there does NOT take away his concealment. Even if you're sure what square he's in, you still can't actually see him and still have a chance to miss.
I should have mentioned that the DM points to another PC, preferably the Cleric.Detect magic is a cone, it doesn't detect things that are "behind" you.DM: X concentrates and begins to pin down the source of the magical emanation...it's riight...BEHIND YOU! *monster attacks*
Which reminds me, since detect spells are cones, remember than they will not get an entire room in one sweep. It will take 2 scans to cover an entire room.
Everyone has already offered stellar advice here, so I don't have a lot more to add, but my rogue player asked for a magic item that activated Detect Magic at will... and I gave it to him. Why?
At the risk of being repetitive...
He still has to disarm the magical trap. And some traps auto-reset. Not all traps are magical--some of my favorite traps are mechanical traps.
As noted, it takes a few moments for distinct auras to form. If they're in a hurry, all they know is "magic is here" which may not be helpful.
Knowing an invisible character is there does NOT take away his concealment. Even if you're sure what square he's in, you still can't actually see him and still have a chance to miss.
Also, don't forget it takes a spellcraft or Knowledge(Arcana) roll to ID auras, which a rogue is unlikely to have a lot of ranks in.
All I have to contribute to this is to respond to the "Detect Magic trumps See Invisibility" argument:
Detect magic MAY, in some cases, obviate the need for see invisibility. It requires three rounds of concentration to do so, and the invisible creatures is STILL invisible-- you'll STILL have a 50% miss chance on any attack you might want to make against it, as you STILL can't see it.
See Invisibility does exactly what it sounds like-- you can now see that invisible creature so your miss chance goes away.
Responding to "Detect Magic makes a Rogue and Find Traps irrelevant:"
Find Traps is certainly a fine spell for... finding traps. Note that it gives a blanket bonus to your Perception checks to locate traps. Once you know it's there, the trap still needs to be disarmed or bypassed in some manner, so it is still an effective threat/deterrent to the party. Please note that Find Traps is useful for ALL manner of traps, where a Detect Magic spammer will only locate magical auras. Fire Trap? Both spells work. Falling block trap? Only Find Traps will help.
In the case of magic traps, you'll still need a rogue to disable it or be willing to spam Dispel Magic or otherwise eliminate the threat. If your party mage makes use of his Scribe Scroll feat to supply himself with a dozen scrolls of Dispel Magic just for this purpose.... why not?
A trap that forces the party to expend resources to progress, but not in the manner the DM intended, is still forcing the party to expend resources.
A trap that casts Summon Monster 2 and calls up 1d3 riding dogs to attack for 3 rounds is obviously intended to provide a mini-combat and/or warning/buffer for the rest of the dungeon's inhabitants. If it is dealt with by a series of Disable Device checks by the rogue-- well, congratulations, that player has just earned their paycheck. If the party's casters use Dispel Magic-- well, congratulations, that's one less dispel in their arsenal, which they really may want in the upcoming dungeon. If they decide to eschew the need to disarm/disable/bypass the trap by exploring somewhere else? That's another choice, with its own consequences.
I fail to see how Detect Magic is in any way game breaking, even in the corner case of "I spend my time concentrating on the door of the tavern, looking for how many auras people have."
Sure, after 3 rounds, you know the number, location, strength, and likely school of each magical aura. Every time a new person enters the room, however, the environment changes and there's potentially a new aura... but you wouldn't know that until at least the second round after they come in, because their active buffs/magic items wouldn't make a blip on your Detect Magic radar if there were any other source of magic in the room already. So yes, if you concentrated on any new arrivals for 2 rounds, you'd know how many auras they had and the strength of the strongest one.... but that's also 2 rounds they have to notice your keen interest in them and react. Furthermore, if that's truly your interpretation, don't forget the door swings both ways.
Let's say there's an NPC cleric who wants to get more information on the party. All they need do is be somewhere they know the party will go (like the inn they are staying at or some similar location) and have Detect Magic up. In only 3 short rounds, they'll have a fairly good chunk of information on what sort of magical arsenal they may encounter later on, and can take sensible precautions against it. Knowing which armor and weapons are magic (and thus where to target their shatter spells, rusting grasps, and sundering attempts), how many consumables the party has (and thus a reasonable idea of their longevity in combat), and so forth would be invaluable information to gain. Combine that with a good Diplomacy and Sense Motive check to gather information about the PC's and size up their fighting capability, and you'd have a damn near complete dossier on them... which any villain with the sort of planning to pull that off would dearly want and take steps to account for. Perhaps the next time the party heads to the streets a gang of street children mob them, attempting to filch as many potions/consumables as possible-- they know where to find them and what to steal, after all, and the party likely won't take severe measures against a bunch of 10 year old kids.
You see where this is going?
If you feel the PC's are using over-powered tactics, remember the door swings both ways. One of the best ways to discourage players from interpreting the rules in what you consider an unfair or broken manner is to apply the same interpretation to your NPC's and to let the players KNOW that's what you're doing.
When it comes to detect magic and using it to detect invisible creatures I don't allow it to out right highlight the invisible creature. As well it takes time and concentration to do it. So not the best if you detect invisibility as the spell.
For finding traps detect magic might alert you to magic in the area but it won't tell you if it's trap. If you study it long enough you can make pretty good guess that it might be.
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Not sure Detect Magic is being adjudicated correctly to "see invisible" creatures or would be economical:
(1) takes 3 consecutive rounds to "locate" aura. You have to study a particular area. Walking into a room won't cut it. AFTER one round of study, you'll just set off your "spidey senses" that magic is in there. You don't know what kind, much less that there's something invisible until you spend the full 3 rounds focused on that particular area.
(2)invisible enemies aren't going to sit there stupidly for 3 rounds as a caster concentrates on his vicinity;
(3) other magic may mask the spell, meaning even if you detect the aura, it may be distorted (DM discretion I suppose).
As for traps, what ever happened to good ole mechanical traps or green slimes, etc.? Useless to Detect Magic.
In summary, have never seen it as a problem.
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I tell my players that its like an arms race if they don't break the spirit of the game and be munchkiny then I won't pazio gave the unlimited cantrips to give a low lvl caster a little more use instead of I cast magic missile and I'm done for the day I tell them its just like scry and die don't do it to me and the.npcs will never do it to you except as plot in a prewritten adventure dictates
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Initially, yes. Then I realized that, in the world of Golarion, any trapmaker worth his or her salt will have a Nondetection cast onto magical traps or secret doors or other things they want kept hidden.
Dude. Even cheaper: just wrap the magic parts in lead foil. 'Nuf said.
On the detect magic vs invisibility.
There is one key line in the DM spell.
You detect magical auras. The amount of information revealed depends on how long you study a particular area or subject.
1st Round: Presence or absence of magical auras.
2nd Round: Number of different magical auras and the power of the most potent aura.
3rd Round: The strength and location of each aura. If the items or creatures bearing the auras are in line of sight, you can make Knowledge (arcana) skill checks to determine the school of magic involved in each. (Make one check per aura: DC 15 + spell level, or 15 + 1/2 caster level for a nonspell effect.) If the aura emanates from a magic item, you can attempt to identify its properties (see Spellcraft).
Magical areas, multiple types of magic, or strong local magical emanations may distort or conceal weaker auras.
Aura Strength: An aura's power depends on a spell's functioning spell level or an item's caster level; see the accompanying table. If an aura falls into more than one category, detect magic indicates the stronger of the two.
Up the the DM to decide if the invisibility spell blocks line of sight or not.
That's all well and good Charender, but if it blocks line of sight I'm hiding behind them :D
Personally I don't mind detect magic being used regularly. More power to the PCs in this case. Gives me 3 rounds to do something else to them, and truthfully anyone can find a magical trap -- only someone with trapfinding can disable one though. So it's not any different than having the party rogue take 20 walking down the length of a hallway to find traps, or having the party barbarian, cleric, etc do it.
I've instituted two caveats regarding detect magic:
1. Use of detect magic to discern the aura of magical traps requires a Perception roll (DC 25 + level of trap spell). In other words, casters are on the same footing as rogues, when it comes to finding magic traps.
2. The effects of invisibility and other illusion spells mask their own telltale auras, until successfully dispelled or disbelieved.
In another thread, Jess Door and others offered an even simpler "fix": change the range to touch.
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Bella Sara Charter Superscriber
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Up the the DM to decide if the invisibility spell blocks line of sight or not.
I would think invisibility would block LOS to the invisible creature/object, but not to the magical aura the invisibility itself sheds.
Sorta like how in MtG, you can target an enchantment on a creature even if you can't target the creature itself.
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Detect magic at will is definitely a big change in the game. I've made some base assuptions when converting older material. The number 1 assumption being that people who are hiding magic stuff know that detact magic is on all the time. If you go to the effort of hiding a wand in a hidden drawer in the back of a desk you are going to know that unless you protect the wand somehow it's going to trivially discovered. So anything that's hidden is assumed to be protected from simple detection with lead or a spell.
As for the rest of it... I rule that detect magic does not work on invisible creatures. I think it's a gray area and rule the way that makes the most sense to me. Even without that a wizard detecting away for 3 round is going to get shanked in a hurry.
Lots of good advice about traps not much to add there except if your players use detect magic as a treasure detector (as mine are prone to) you can easily use that as bait for a trap itself. I've had one player repeatedly get himself into trouble trying to chase magic items. I relish the idea of hitting him a few more times... bwhahahaha
The simple fact is that when a party's abilities change, the challenges they face have to evolve as well.
When the final rules were released, there was much wailing and gnashing of teeth over unlimited Detect Magic, mostly by those who resented their time honored and cherished DM tactics being rendered obsolete and who refused to consider new ones. Most DMs just shrugged and went to work figuring out ways to either counter the new ability or incorporate it. That's part of the challenge and the fun of being a DM, IMHO.
When a party gains access to Invisibility, what was once a challenge no longer is. Same with Fireball, and Teleport, and Scry. Higher level intelligent opponents will develop different defenses for different tactics. If they didn't, then they wouldn't survive to become higher level intelligent opponents. Even the much lamented Scry and Die tactic is ridiculously easy to prevent, counter, or co-opt by some pretty simple BBEG (or party) tactics.
The long and the short of it is, the game has changed, and DMs have to be willing to change with it. Or not. That's what House Rules are for.
No offense intended, but I think that if your game is being unraveled by Detect Magic then you are probably using magic traps the wrong way.
Magic traps are not supposed to just be tossed everywhere so that the Rogue has something to do. They are supposed to be a part of the drama so that the Rogue is racing against the clock to disarm them while something else is happening.
So the idea where the PCs are being chased and there is a field of magic traps is a good idea. The trick is to just let the spellcaster find the traps and the rogue disarm them, because that's just good problem-solving.
But for things like doors where there is no action, you need to be more creative. For example, you could have a combined mechanical and magic trap where a pressure plate slides a lead-lined panel back and reveals a symbol or something, or a floor that breaks away and drops you into a pit with a permanent cloudkill.
The idea is to not punish players for using their abilities, but to mix it up often enough to inspire fear when they make those trapfinding rolls.
In my games, I treat constant casting of any 0 level spell the same...
"Ok, after about 10 minutes or so, your hands and arms are beginning to get tired from the constant somatic components, and your voice is starting to become hoarse from the verbal components".
Just because there are no rules to stop this kind of silliness from happening doesn't mean common sense shouldn't be applied.
As a side note, I also treat Detect Magic vs Invisibility the same as I would treat Auspex vs Obfuscate in Vampire: the Masquerade... a 0 level spell just isn't powerful enough to piece the veil of invisibility of a 2nd level spell. I may allow Arcane Sight to do so, though.
Also, don't forget it takes a spellcraft or Knowledge(Arcana) roll to ID auras, which a rogue is unlikely to have a lot of ranks in.Everyone has already offered stellar advice here, so I don't have a lot more to add, but my rogue player asked for a magic item that activated Detect Magic at will... and I gave it to him. Why?
At the risk of being repetitive...
He still has to disarm the magical trap. And some traps auto-reset. Not all traps are magical--some of my favorite traps are mechanical traps.
As noted, it takes a few moments for distinct auras to form. If they're in a hurry, all they know is "magic is here" which may not be helpful.
Knowing an invisible character is there does NOT take away his concealment. Even if you're sure what square he's in, you still can't actually see him and still have a chance to miss.
Yeah, he doesn't try to id what kind of aura, just to see if something magic is there (the other three members of the party are spellcasters, so if he sees something weird, he can always have them take a look and try to identify it).
Yeah, a close reading of the spell told me that the caster must spend the time studying the area or object, so they can't walk around with the round-3 effect (exact location) to be ready the instant they walk in the room. But in the one case it mattered, the invisible enemy took a couple rounds stealthily moving into position for a melee attack, at which time he was lit up.
I think you're forgetting something (2 somethings, actually):
1. Duration = Concentration.
2. Area: Cone-shaped emenation (60')
So, in the opposite order, let's look at #2 first. If the invisible attacker steps outside that cone in those 3 rounds, the mage loses him.
In fact, if the guy moves out of the cone it in the first round, the mage wouldn't even know something is up, because round 1 just said "Yup, there's magic" - if there's any other magic in front of him, (like a party member with any item, say) the sense is still the same.
If he does it in round 2, the mage would suddenly notice there's one (or more) fewer auras in his spell... BUT...if he turns to find it, he's back to round 1 (and he's not sure what way the guy went, because he's still not got locations, so 50% chance of failure there) -- best case, all he can say is "There's magic somewhere in the cone in front of me!"
If he does it in round 3, the mage will have an idea of what direction the guy went, but it's still a reset to round 1 (so the invisible guy can just move and get out of the way).
In addition to all that.... The mage needs to make concentration checks whenever he gets hit, runs, etc, etc. Plus, concentrating means that he can't cast other spells. If he loses concentration, it takes him 3 turns to get the spell back up to a point where he gets locations.
So, you know, I don't really think it's that big a deal.
In terms of your magic trap issue, well...
This is almost completely solved by Magic Aura. If you're going to bother with putting up a magic trap in the first place, who wouldn't then slap a fake "Arcane Lock" on the whole door to mask the traps?
Yeah, but a few shouts of "IT'S RIGHT HERE! IT'S RIGHT HERE! GET IT OFF ME! AAHHH!!" will do wonders for pinpointing a square to attack.
In this case, I'd say that an intelligent invisible creature would probably hit the mage hard and then take a 5' step out of the cone. He might lose concentration, does lose your location, and if he calls out a square, he's likely wrong.
And, as others have suggested, my GM has instituted the "Invisibility prevents line of sight" to the invisible thing, thus making the DM for See Invis pointless -- though he didn't really need to. [We also play that illusions is to say that they contain misleading things in their auras, so, for instance, if there's level 3 illusionary wall your level 0 detect magic comes back with "That wall is enchanted!" as opposed to "Look, an illusion!"]
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Pshaw, I houseruled that you can't see through any barriers, and it can't beat higher level illusion spells with detect magic, so if there's a wand covered by a cloak, nope don't detect, basically that if you can't see it, you can't detect it. I think that's a little better than the houserule of touch because sometimes there's things you want to detect that you don't want to touch if they aren't magical (Anything Mammy Graul touches)
You want to detect magic instead of looking for traps the old fashioned way? Ok, you found something. Illusion school. Seems to be concealing the actual trap mechanism.
P.S. Phantom Trap. About that only thing that'd work against it is Dispel Magic.
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i don't know if this has already been said (i didn't feel like reading the entire thread):
#1 problem with this is: but even if one person can spend 3 rounds to detect an invisible creature (make sure the invisibility is supernatural first and not extraordinary), but simply knowing the correct square to attack an invisible target still gives him a 50% miss chance. If he pin-points the creature him self, all he can do is point to the correct square.
#2 problem with this is: if the invisible creature moves, he has to spend 3 more rounds to pin-point him if he hasn't moved outside of the cone
#3 problem with this is: i have come to a census myself the detect magic to detect magic traps is a problem. So, i simply allow them to use detect magic to add +5 their perception bonus to detect magic traps. Sense most mages I've played/GM'ed for never take ranks in perception anyway, this isn't a problem. A level 1 magic trap has a perception DC of 26.
#4 problem with this is: you might be getting too worked up over finding magic stuff at the bottom of the water. That IS after all the EXACT use Detect Magic WAS intended for. (they'll still miss the mundane stuff like art, gems, and masterworked gear).