I have not had a defined Aqua Cranial session but have played around with doing CST in oceans and pools with friends. It seems like a natural extension and the 3D, weightless environment allows for great comfort of ease of both practitioner and client. Doing CST in an ocean adds the wave motion making for a more dynamic session. Then they throw in the dolphins!

Upledger has been doing dolphin/cetacean assisted CST since 1996:
www.massageandbodywork.com/Arti....html

What intrigues me most about the aquacranial website is the extent they have taken this , looks like cool stuff. I would think a class in Watsu would give you a good foundation for approaching the client, safety etc. Are they doing watsu at Breitenbush Hot Springs yet?

I've done some bodywork of differing sorts in a float chamber, cranial work is very effective in that environment.