on a walk through the drone hall of CES I found some underwater vehicles and took some pictures.
Probably some inspiration.
Thunder-Tiger (had BR-thrusters last year ) Uses QGC
Prototype (with flying drone gimbal inside)
Biki, mini finning diving fish. Interesting ultrasonic underwater Hand controller
Sublue, Chinese manufacturer with many designs
CCROV, with some interesting design Details (e.g. power over tether)
Ok, thats it in summary. Hope you like it.