12L it is.
I've googled a bit on Lipo and H2O - I guess not a good mix, but it would provide for colorful fireworks display

Since I have to start from scratch - what are the good batteries to get?
I only toyed with small scratch built airboats (running LiPoly) and really have no idea what runtimes to expect from 12L / Jet Drive. Quicksilver what's the mAh rating of your pack and how long were the run times on your jet boat with 700sc?