To put it simply, zoans and other fruits that give potentially permanent transformations should not revert when in water. This is completely contrary to the source material. The main example being Chopper. When Chopper falls into or is submerged in water (Chapter 413) he remains in "Brain Point." This is not Choppers true from, but a devil fruit transformation. Choppers true form is his "Walk Point" and if his transformations turned off in water, he would revert to this form. I believe this is because water simply weakens the user, it does not negate df abilities. Meaning, that any ability or transformation that the user doesn't have to actively focus on will stay active if the user is underwater. That's why all of Big Mom's homies didn't disappear when she fell into water at Wano. Another precedent for this is with Luffy at Arlong Park. Knowing what we know about the true identity of the Gomu Gomu no Mi, Luffy was still able to stretch when he was submerged at Arlong Park. He couldn't move himself, but Nojiko was able to stretch him as to allow him to breathe by pulling his head out from the water (Chapter 86). Under the assumption that Zoans revert when in water, Luffy as a Zoan user and not a Paramecia user should have reverted to his original form and not have been able to be streched.
TL;DR Zoans should stay in transformations when in water just like Luffy and Chopper.