Now that reminds me of the Turtle.
James,
I don't know about solar panels for recharging batteries, but Kittredge's latest work has been on a human-pedal-powered/sail-powered sub he calls the UEM for "Ultimate Exercise Machine". So there are definately alternatives out there.
Jon
A thought occured to me. Being that a gas engine is not a good idea to put in a psub, why not put in a small diesel, to reacharge the batteries. And as a second thought, being that I am pro environment, how about adding solar panels to also recharge batteries?
James Huffman