I had a sub. that was not R/C, but it as battery powered, and it dove too. Way cool.
Mine barely floated, it was almost neutral bouyant. It took two C-cells.
What it did was dive fror about 3 feet, the dive planes would turn, and it would rise to the surface and dive again. It was a replica of an older sub. Almost cigar shaped.
What was killer, We would take to the local lake, my father and I would stand paralell to th shore about 10ft away, and we would watch it dive and rise, cathch it and turn around. All in all a lot of fun. Not R/C but definetly fast, and battery powered.
I can imagine one of 401's camera's on one eh?
**edit**
Along those lines, bfeore I was into R/C I found and R/C sailboat while snorkeling. A big long one, about 4 feet long, huge mast. I wish I would have saved it (the mast was broke I think that's what sunk it) If I can find stuff snorkeling I can only imagine what you could find with a sub heh