
Create Mr. Pitt |
So level 13 conjuration teleporter we're about to go on our first underwater adventure. Our fighter has great swim, necklace of adaptation, and darkvision. Neither our bard or swashbuckler have any swim skills, so I will prepare a ride the waves for both of them and darkvision.
We were given the ioun stone that lets us breathe underwater, so it seems like a waste to use another ride the waves on myself, so I will concentrate on swimming when possible, teleporting when necessary, and can always give myself a swim speed in a pinch. (And a safe interdimensional space for sleep as necessary)
I have plenty of aquatic SM spells, strong conjuration bf control, usable damage spells, and plenty of empty slots to prepare. Any suggestions for a caster with 7th level spells for an under the sea adventure (my goal is not to directly skip the adventure, a colossal dire shark is present enough for me). But any suggestions about spells that might be useful would be appreciated.

Avoron |
Elemental body IV would be an excellent self-buff spell: +8 Con, +6 natural armor, 120 foot swim speed, DR 5/-, loads of immunities, and the ability to create a vortex, all without losing the hands or speech you need to cast spells. And it lasts 13 minutes, which is a very manageable time for use before combat.
Buoyancy could be incredibly useful for emergency escapes: it lets several creatures shoot up to the surface from any depth and only takes an immediate action to cast.
Freedom of movement is a classic for underwater combat, it couldn't hurt to have that prepared.
Assuming you typically use fog spells, twilight haze could be a nice underwater substitute, doubly so if you make shrewd use of true seeing.
Heavy water is the ultimate underwater battlefield control spell, effectively freezing enemies in place in a vast area by requiring a full-round action to even attempt to move at half speed. Sadly, it's not on the wizard spell list, but if you can get your hands on a scroll or something, it could be very effective.
Finally, how about elemental bombardment, just for fun.

Create Mr. Pitt |
I definitely considered elemental body iv, I get 14 minutes with the orange ioun stone, but I am a bit of a concerned about being such a massive target. Also I might just go small water elemental, save my seventh level slots and get the 60 ft swim speed (though the 120 is appealing).
The prospect of using buoyancy as an offensive spell is really interesting. It can also serve to safely get us home, but it could also be like targeted reverse gravity in water. Divide and conquer. Good stuff, thanks!

Avoron |
Using buoyancy offensively would be interesting indeed, although it only takes a DC 20 swim check to avoid being pulled upward, and most CR-appropriate aquatic enemies will make that without blinking an eye.
As for turning into an elemental, this might be a bit of a crazy idea, but have you considered planar binding an actual elder water elemental and possessing it? It's completely free, and as simple as drawing up a magic circle, spending 10 minutes to cast the spell, and setting fire to everything in sight (just in case0. It's not like you'd have to be that concerned about it resisting, what with it's whopping Cha 11, Will +5, and SR 0. Summoning elementals for a day and letting them go is probably the least abusive possible use of the spell, so it shouldn't be too much trouble. Possession will last a comfortable 14 hours, so you can just leave your body hidden on dry land while you go adventuring as an elemental.
Finally, an elder water elemental's stats would make a really great chassis for a caster on an underwater adventure. Swim 90 feet, darkvision, high Dex and Con, plenty of natural armor, 15 foot reach for touch spells, d DR 10/-, and a whole slew of great elemental immunities. Plus, looking like yourself again is always just an alter self spell away. What's not to like?