I just had a bit of an idea about making a mermaid kigurumi for underwater/pool/tank performances. Of course this would require some training to use but what if the mask's eyes were built on top of tinted swim goggles or a diving mask. A mini re-breather or snorkel inside would allow the performer to breath. The hada would have to be made out of the same material as wet suit instead of spandex or lycra. The tail would be built in with a monofin at the end along with some webbing between the fingers to improve mobility. Not sure about any padding yet since I'm not aware of any suitable material for the task that isn't buoyant. As far as the zipper goes maybe have two magnets, one in a key of sorts or inside the suit's fingers and one on the zipper pull, to make it easy to unzip when wet as well as keep the illusion without a large pull tab. I am aware it will be more expensive than a normal kig but it's only an idea hat could be implemented if someone was willing to make it.