It is known that the Yomi Yomi no Mi fruit will only revive its user once, and also that Devil Fruit users can't swim, so I was wondering... What would happen if Brook falls into the ocean? I mean, even if he's alive, as a skeleton he has no lungs, so he should just be unable to go back to the surface, shouldn't he?
He's just a skeleton obviously, so he's not really breathing, however, when his body gets drowned slowly by the seawater, his strength begins to fade away (Chapter 493, page 7):
And from this scene, I imagine if he falls into the ocean, like all Devil Fruit users, he will be powerless and be unable to resurface unless helped.
I imagine it would work something like this:
As a Devil Fruit user, he'd be rendered weak by the submersion. But we've also seen instances of Devil Fruit users' powers being somewhat nullified by submersion in seawater (specified since I have no idea if it applies to bath water, pool water, etc.). For example, Luffy was unable to stretch himself in the Arlong Park arc, but his head was still brought above water by third parties. Similarly, in the Enies Lobby arc, Chopper's rampage was stopped when Franky threw him into the sea, transforming him back into little Chopper.
My thought was that since Brook can't drown, as he has no lungs, the fact that he was submersed in seawater would nullify his Devil Fruit power and his soul would leave his body at the bottom of the ocean.
Just a thought.
Like all Devil Fruit users, Brook won't be able the move if he is fully submerged underwater, that's a fact.
But will he drown? We've seen Jack the Drought Mammoth guy got trapped in the sea floor still alive but unable to swim himself up, waiting for someone to rescue him because he was a fishman-human hybrid. We don't know whether Brook will drown or not because, during Fishman Island, he was wearing an oxygen bubble underwater, meaning he somehow breathed. Otherwise, he wouldn't need it since he was fully submerged in the water anyway (episode 538).
I always theorized that Brook had invisible organs that could not be touched or felt since he eats and poops, and that requires organs to break down his food and give him energy like all living things. If my theory is correct, then Brook will drown underwater.
As a skeleton, he has no lungs to drown with. As a Devil Fruit user, he cannot move underwater.
You can make theories about how he works all you want, but as far as we've seen, there is no proof that he can die unless you destroy his skeleton. And even then, we've seen him pull his head back on using his spirit.
It is a known fact that skeletons decompose in salt water, it just takes five or ten years to accomplish. However, we've seen Luffy attack people while his limbs are underwater (Fishman arc) using Haki to protect his stretchy arms, so I'd assume that if Brook ever learned full-body (or full-skeleton?) Haki, he could not only survive the ocean but even walk about underwater unharmed. Swimming I doubt, as he has no flesh to move the water out of his way with. But would he survive? Most certainly.
So to sum it up: Brook COULD survive underwater for five or ten years in paralysis, or indefinitely (or as long as Haki lasts) with full-body Busoshoku Haki.
Michael brought up the topic of Luffy when nullified. He did tell his Devil Fruit being nullified underwater but was used by a "third party", so Devil Fruits can still function but the user is paralyzed I think.
So if Brook goes underwater, he doesn't drown because he's breathing nothing literally, so he won't drown. But let's say maybe he's underwater like Luffy. Just like drowning in a dreamlike situation, but he's unconscious like having a battery used 5x faster so it'll be null. But Brook won't die, he'll get unconscious, like "unconscious mode" underwater, so he'll be unconscious only. Even if he ejects his soul in the body because the body is the source of him.
And by Luffy, as his Devil Fruit abilities are still going to be functioning by other people as a third party, well, I don't know about Brook, but he's still having his abilities, but he's like paralyzed.
I think you asked this question because you have seen Brook running on water. No, Brook isn't actually able to drown as he has eaten a Devil Fruit, namely the Revive-Revive Fruit, but he can't die as he is already dead. As per Brook's statement, when a person who has eaten this particular fruit has died, his soul would have to descend to Earth and find its body to be revived. But Brook happened to die in the Florian Triangle, which was so engulfed in darkness that Brook's spirit had trouble finding the body. And when he finally found it, Brook had already turned into a skeleton.
But we also see that Brook is able to literally "run" on water. This is because he is a very light-weight person. But of he were to stop running, he would immediately sink.
Had Brook's spirit found its body before he became a skeleton, then Brook wouldn't be so light as he is, thus he wouldn't be able to run on water.
So, if he is dropped into the ocean, he can survive by running on the Ocean's surface. But if he is released under the ocean like from a submarine, then he would lose his strength, but we can't say that he would die cus he is already dead.
It was a Skull Joke