I’ve been a fan of One Piece for over a decade now, and in that time, there has been one question I’ve wondered about and been asked by new fans and friends countless times: if Devil Fruit users can’t swim, does that mean that there can’t be aquatic Zoans? Logically, an aquatic animal has to be able to swim, so the Devil Fruit must not give the option to become a fish or anything else that’s not specifically a land animal.
I only just realized it recently while writing another theory, but Oda actually answered that question back in 2012, I just didn’t know enough about biology or zoology to know that he had. Aquatic Devil Fruit do exist, and we’ve already seen one: the Sala-Sala Fruit, Model: Axolotl.
Until recently, I was under the impression that axolotls were semiaquatic salamanders, able to leave the water and walk on land as they pleased, but this is not the case. Axolotls are actually fully aquatic, being born in the water and living their entire lives there. They are technically capable of going on land, and often end up jumping out of the water in an overzealous and poorly judged charge, but they are not made to be on land. Their limbs are not adjusted for properly walking on land, their feeding mechanisms require they be underwater, and their gills (the frills on the side of their heads) are made to draw in oxygen from water, not air. If they are kept moist, somehow have a food supply, and aren’t eaten by predators, then they could potentially survive, but all of those requirements are simply not feasible.
So if there are aquatic Zoans and aquatic animals can swim, aquatic Zoans must be able to swim then, right? Wrong. No Devil Fruit user is able to swim, and aquatic Zoans are no exception, as evidenced by Smiley’s aversion to water.
If Smiley were able to swim, he wouldn’t have had to break himself into pieces and spit them across the lake to cross it. One could argue that this is because he’s made of slime, and would have dissolved in the water had he attempted it, but in that case he could have taken his full axolotl form which wouldn’t have been in danger of dissolving. Yes, he would have been in danger of freezing in this particular case, but that’s situational and wouldn’t constitute disliking water on the whole as Caesar claims Smiley does. Therefore, Smiley’s aversion to water must be due to his Devil Fruit, not his chemical makeup or the extreme temperatures of Punk Hazard.
So the aquatic Axolotl Fruit doesn’t allow the user improved swimming abilities, but it must give the user some kind of ability. Given the natural abilities of axolotl, I can personally think of three.
1. The user may be able to breathe underwater, though they cannot swim. People who can breathe underwater naturally don’t drown after eating Devil Fruit, they just become paralyzed, as we saw with half-fishman Jack the Drought.
It seems obvious to say, but Devil Fruit users only drown when thrown in water because they can’t naturally breathe it, not as an automatic side effect of the Devil Fruit. Therefore, an aquatic Zoan, which will have gills, will have the ability to take in oxygen from the water, just not to move around in it.
Of course, that’s assuming that they’re in their hybrid or beast form when they fall in. If they are submerged in water, then they cannot transform, as being underwater disallows a Devil Fruit user from activating any of their abilities. In the case of Zoans, however, being underwater does not deactivate an already active ability, as demonstrated by Chopper staying in his hybrid form whenever he is underwater instead of reverting to his default beast form.
There have been multiple times where Chopper has found himself underwater, and as far as I could find, he was always in his hybrid form before and after being submerged, which shouldn’t be possible if the water deactivates Devil Fruit abilities. [I believe Oda actually addressed this in an SBS at some point, but I couldn’t find it. If anyone does find it, please alert me and I will edit this section as needed.] Similarly, when Momonosuke was submerged on Zou while in his beast form, he did not revert to his default human form.
Therefore, if an aquatic Zoan were to be in their hybrid or beast form before falling in, they should theoretically stay in it while underwater, though they cannot change to their other forms until they return to the surface. So long as they aren’t in their human form (or slime form in Smiley’s case) they should be capable of breathing underwater, despite not being able to move.
That said, Chopper did revert from Monster Point back to his hybrid form when submerged in water, but that may well be because Monster Point isn’t a natural form of the Human-Human Fruit and he was in his hybrid form before entering Monster Point.
Either way, Chopper did not revert to his default beast form, so the point stands that a Zoan user will not return to their pre-Devil Fruit form when submerged in water.
2. The user may have advanced regeneration abilities. Salamanders in general are reportedly the most adept vertebrates when it comes to regeneration, able to regenerate lost limbs and organs, both internal and external. Given enough time and the proper circumstances, salamanders can regenerate from just about anything if there’s enough of them left to do it. This is ability is probably augmented by Smiley’s fluid slime body, which doesn’t have complex structures like bones or organs to worry about. This ability is probably universal through all models of the Sala-Sala Fruit, but it would still be an undeniable perk for an otherwise fully aquatic Axolotl Fruit user.
3. The user may be able to alter their pigments for camouflage. Axolotl can change colors to match their environment, but only a very limited amount. In the context of One Piece, though, it may be tantamount to turning invisible.
4. The user may be able to create a powerful vacuum of suction. Axolotls, being fully aquatic, feed via suction, drawing in their prey so they cannot escape. Though suction feeding requires water in real life, the user of the Axolotl Fruit, especially if they’re as big as Smiley, could probably draw in massive amounts of air, pulling anyone or anything not tied down towards them. The user might even be able to weaponize the drawn in air, shooting it back out as a pressurized cannonball of air. Though there are many fish that suction feed, as far as I know the axolotl is the only salamander that does, so this may be the unique ability of the Axolotl Fruit that the user’s fighting style would center around.
Axolotls may have other abilities I’m not aware of, but as far as I know these are the skills they are most well known for. Similar logic would probably be applied to other aquatic Zoans, so as long as they have unique abilities, weapons or defenses, they would be useful despite being forced to stay on land.
Octopus or Squid Zoans would undoubtedly get tentacles, and depending on the species they could have ink, poisons, barbs, or perfect camouflage capabilities.
Aquatic mammal Zoans such as dolphins or whales could have sonic abilities, using echolocation as a sort of pseudo-Observation Haki or even launching sound attacks, or in the case of whales they could even just use their overwhelming size as a weapon.
Angler Zoans may have a hypnotic lure, Shark Zoans may have powerful teeth and rough skin, Jellyfish Zoans may have neurotoxic tentacles, and Ray Zoans may have a stinger or may be able to use their kite-like fins to catch drafts and float.
Depending on how Oda wants to take it, that could well be the ability of all aquatic Zoans that don’t have the ability to move on land: the ability to manipulate their swim bladders or oily livers (depending on if they’re bony or cartilaginous) or other flotation mechanisms to become buoyant in air, allowing them to swim. I’m not sure if Oda would do this, considering that mermaids don’t seem to be able to do it, but Devil Fruit magic is a mysterious thing, so I really wouldn’t be surprised.
If Oda really wanted to get crazy with it, though, he could have a Carp Zoan with powerful jumping abilities that turns into a dragon when it jumps high enough, mirroring the legend of the carp that jumped over a waterfall to become a dragon. This could potentially be a Mythical Zoan or possibly even part of the Awakened form of the Carp Fruit.
There are also a number of semi-aquatic Zoans that already exist, such as the Snake-Snake Fruit, Model: Anaconda…
…the Turtle-Turtle Fruit…
…or even the Crab-Crab Fruit that Oda had originally planned to give to Inazuma.
All of these semiaquatic Zoan Fruit would allow the user to move while on land while having the potential to allow the user to at least temporarily survive underwater. The Crab-Crab Fruit could also have alternate models to cover all kinds of crustaceans, each with durable shells and unique claws, ranging anywhere between the standard cutting pincers of a crab, the bubble cannon of a pistol shrimp, and the powerful smashing fists of a mantis shrimp.
There are countless possibilities for aquatic Zoans, regardless of the fact that they clearly would be incapable of swimming in water like their natural counterparts. Whether they can swim in the air, have the weapons of their counterparts, or just have protective scales and nothing more, aquatic Zoan Fruit would definitely have their uses and be just as much of a force to be reckoned with as their terrestrial or aerial counterparts.
*Theory by Tokiro Oumaga