I'm sure it wouldn't be worth it, because otherwise people would be doing it, it just seemed like a cool way to supplement solar or even to allow for indefinite

I'm sure it wouldn't be worth it, because otherwise people would be doing it, it just seemed like a cool way to supplement solar or even to allow for indefinite underwater drones. Like, imagine a deep-sea research drone that could spit out an anchor and recharge whenever the battery got low. Almost certainly a case of "Cool, wouldn't really work well"