Hmm, Aquatic Marisas can't handle any form of water, they can only float on it, and as much remain small to make it easier to live floating on water.
Unless they are True Aquatic Yukkuris like the Nitoris or Murasas, then yukkuris will be affected by water, i think only those 2 are truly waterproof, the rest aren't, even the Suwakos for some reason.
Maybe you can compare Aquatic Marisas with those animals that can float on water but can easily drown if you ruin their method of flotation.
Also they are pastries so unless they have the waterproof magic that nitoris and murasas have, expect them to dissolve in water after prolonged exposure.