I am no 'battery' expert either, but yeah I do know that if you get salt water on NiMH batteries some nasty gases come out and the get hot!
Then again, hopefully water doesn`t get inside; that isn`t part of my plan!
HAHA
Anyway, I`ve now written a set of intructions on how its built; check out my blog.
www.dolphinscuba.com.sg/blogs_wp/