Basics:
how big is it going to be?
Right now it's looking like its going to be close to a 120 mm cube.
What material did you print it out of?
Right now I'm using PLA printied at 100% infill. The parts seem to be negatively buoyant.
What printer did you use?
I have a printrbot simple metal with a heated bed.
Whats your plan for motors, etc?
Right now I'm using some old 12v radio shack motors that were for the original sea perch design (I wanted to make an ROV for a really long time).