Not normally.
Grapple is a standard action. Attacking once is a standard action. Attacking more than once is a Full-round action that consumes your standard action. You only get one standard action per turn, so there is no way to grapple and make another attack which would require two standard actions.
There are some feats out there that can influence this, but not typically available to your ordinary mollusks.
The Octopus and Giant Octopus, as well as the Squid and Giant Squid all have the Grab ability, which states that the creature can attempt to make and maintain a grapple with just that one appendage at -20 CMB. So yes, in theory, a regular Octopus could grapple a maximum of 1 creature in a turn and a Giant Octopus could grab a maximum of 8 creatures in a turn. Due to the Giant Squid not being humanoid, the rules on whether it can use its arms to separately grapple creatures on the same turn is unclear.
EDIT: To clarify, the Octopus only has 1 "tentacles" attack with the "grab" ability, the Giant Octopus has 8, the Squid has 1 and the Giant Squid has 1 as well as 2 "arms" that do not have the "grab" ability. I mentioned the part about humanoids because the Grapple section in the CRB says humanoids without 2 free hands are at a disadvantage to grapple.
From what I understand, the new leading theory is that the creature (a giant octopus for instance) will attack you with its tentacles, attempt to grab, if successful it applies constrict damage, release the grapple as a free action, and then use its next tentacle attack to do the same.
Not normally.
Grapple is a standard action. Attacking once is a standard action. Attacking more than once is a Full-round action that consumes your standard action. You only get one standard action per turn, so there is no way to grapple and make another attack which would require two standard actions.
There are some feats out there that can influence this, but not typically available to your ordinary mollusks.
This isn't really relevant because he's talking about creatures with the grab special ability, though he spelled it as grap in his initial post. Which I think you mistook as being short for grapple.
Grab (Ex) If a creature with this special attack hits with the indicated attack (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity...
The grapple after the attack is a free action that does not interfere with the full action attack. After hitting with the attack, the mollusk must decide to grapple normally or to use that single appendage.
If it grapples normally it will gain the grappled condition, but can continue attacking with its other attacks at the -2 penalty from the grappled condition. If it takes the -20 penalty to only grapple with the single appendage, it can continue like nothing has happened.
So yes, the mollusk finishes its full attack.
(I can't comment on the terror of Claxon's tentacle hit, grab, constrict, release suggestion. The RAW checks out, no idea if this was an intended mechanic.)
Sorry, I should have thought my first post through more thoroughly.
The little mollucks use all their tentacles at the same time: one attack that uses multiple tentacles (which might hit for slam damage) with one GRAB (which allows a free grapple check) - they don't make separate tentacle attacks at different (or the same) targets.
The giant octopus is an exception. It uses each tentacle separately and could attack 8 different foes if they're within reach, doing slam to each target and using GRAB on each target separately. But then NEXT TURN it's screwed because it takes a standard action to maintain ONE grapple and has to release all but one of its victims. Worse, if it maintains that ONE grapple, it has used its standard action and now it can make no other tentacle or bite attacks this round.
The giant squid is somewhere in between - it uses its tentacles like the little mollusks - one attack using a bunch of tentacles and initiating one GRAB. It also has two separate arms that can slam but cannot GRAB, so it could make 3 attacks at reach (a 4th attack if anything is close enough to bite), but only one of those can GRAB. It has the same problem as the giant octopus on the next turn - if it wants to keep grappling, it cannot use its bite or arm attacks.
I personally am not a fan of ANY creature that is built for grappling, especially low-INT animals, doing the grapple-let-go-grapple-let-go-grapple-etc. combination attacks. That's just not how nature works. If a monk wants to do that, or other intelligent creatures who learned grappling, fine, that's a good plan. But creatures who naturally grapple by instinct just don't let go. Ever. Until they win the fight (and then can enjoy their meal) or lose the fight (and either die or try to run away).
But, personal fan or not, the Giant Mollusks are definitely more effective if they NEVER try to maintain grapples - just release as a free action immediately after each successful GRAB.
Hmm, I see how you're getting there, but I disagree, DM_Blake. The Grab ability states:
The creature has the option to conduct the grapple normally, or simply use the part of its body it used in the grab to hold the opponent. If it chooses to do the latter, it takes a –20 penalty on its CMB check to make and maintain the grapple, but does not gain the grappled condition itself.
I think the Giant Octopus can attempt to maintain its 8 grapples indefinitely. At -20, the odds of it actually being able to grab with all 8 the first round are low (even with its +19 grapple CMB), and the odds of maintaining them all are miniscule, but it seems to be a possibility. That being said, if it manages to make half of its first grapple checks and manages to maintain half of the subsequent checks, that's 2 opponents grappled while still being able to do full-attack actions each round. Not a bad trade. It'd be extremely effective against low-level creatures but most on-level creatures would have the CMD to avoid it or break free, which honestly sounds exactly like what you'd expect from an iconic aquatic encounter. The red-shirts get tossed about and pummeled with ease while the heroes wade in and take care of business.
Your quote of the GRAB ability never says what action is required to hold the opponent. It doesn't turn this into a free action (if it did, it would need to explicitly say so).
But the Grapple rules in the Combat section are quite explicit about what action is required to maintain a grapple: Standard.
So GRAB tells you that you can do one of two things:
1. Conduct the grapple normally. You and your victim both get the Grappled condition. Each round you can maintain the grapple as a standard action and if you do, you can do the usual stuff (damage, move, pin).
2. Hold the victim with your body part (e.g. octopus tentacles). If you successfully GRAB at -20, only your victim gets the grappled condition, you do not. Each round you can maintain the grapple as a standard action at -20 on the check and if you do, you can do the usual stuff (damage, move, pin).
Either way, normal grapple or simple hold, it's a standard action to maintain it. If you want to maintain two grapples, you need two standard actions.
The Greater Grapple feat lets you maintain a grapple as a move action. Theoretically, if our cuddly mollusk were to have this feat, it could maintain two grapples each round, one as a move action and the other as a standard action.
Added Gwen's edit for clarity.
Drifting off topic and exploring how creatures with grab and several attacks are intended to be played: As far as I can tell, there is nothing in the grab -20 rules that lets the Giant Octopus maintain the grapple for free in the following rounds. Does this mean that the Giant Octopus that grabs 8 sailors in its first round must maintain only one of the eight grapples as a standard action (or drop all of them as a free action, then full attack)?
P.S. Thanks for elaborating on the little mollusk single tentacle attack DM_Blake, I missed in the wording that it only had a single grab attack.
Your quote of the GRAB ability never says what action is required to hold the opponent. It doesn't turn this into a free action (if it did, it would need to explicitly say so).
But the Grapple rules in the Combat section are quite explicit about what action is required to maintain a grapple: Standard.
So GRAB tells you that you can do one of two things:
1. Conduct the grapple normally. You and your victim both get the Grappled condition. Each round you can maintain the grapple as a standard action and if you do, you can do the usual stuff (damage, move, pin).
2. Hold the victim with your body part (e.g. octopus tentacles). If you do, only your victim gets the grappled condition, you do not. Each round you can maintain the grapple as a standard action at -20 on the check and if you do, you can do the usual stuff (damage, move, pin).Either way, normal grapple or simple hold, it's a standard action to maintain it. If you want to maintain two grapples, you need two standard actions.
The Greater Grapple feat lets you maintain a grapple as a move action. Theoretically, if our cuddly mollusk were to have this feat, it could maintain two grapples each round, one as a move action and the other as a standard action.
One minor edit on number 2:
You have to start the grapple with -20 for number 2 to apply ("–20 penalty on its CMB check to make and maintain").I realize you were talking about maintaining in your response, but with that one minor edit, this is a really good summary of the rules that can be copied and used outside of this conversation.
Just to be clear, I'm trying to say that the first grapple check to maintain would take the standard action, and only the subsequent grapple checks to maintain would be free actions.
By strict RAW, I must concur that it does not actually allow for maintaining multiple grapples as free actions, but that's how I would advise house-ruling it. Why? Because the scenario looks much sillier without it, and breaks verisimilitude for me (I know, I know, different strokes for different folks…). By RAW, the Giant Octopus should drop all 8 theoretical enemies at the beginning of its turn as a non-action (failure to maintain a grapple), and then do its full-attack and grab them all over again. Imagining that scenario in my head, it looks much sillier and more convoluted than just maintaining the extra grapples as free actions (that require CMB checks, obviously). Attack, grab, constrict, drop, attack, grab, constrict, drop… It seems incongruous. I would much prefer: Attack, grab, constrict, constrict/drop/move/pin.
If you were an actor on a set, being attacked by a giant animatronic octopus, wouldn't you think the director/producers/writers had all gone insane if they kept having you picked up and dropped every few seconds? As roleplayers, we're essentially the actors, playing our characters in a collaborative story.
If we're getting into house rule territory, just create an Improved Grab feat which allows maintaining any and all grapples that started with a GRAB to be maintained as part of the same action each round, so if you have more than one enemy grappled, you can just burn your standard action to maintain all of them, or if you have Greater Grapple, then you just burn your move action to maintain all of them. You still need a separate CMB roll for each grapple you maintain.
Then swap out one of its silly feats (why does a giant octopus have Iron Will, anyway?) for this feat and now it's deadly - grab a bunch of victims and then swim off to the deep water to crush/drown them and have an all it can eat buffet.