As a player who uses spells unconventionally, I say sticking your hand into water and unleashing electricity to kill your enemies is asking for the GM to say "how much electricity resistance do YOU have?"
Also? what about the fish? I'm pretty sure there are creatures out there *cough* akhana *cough* that regulate creature's life and death that would be upset if people start killing creatures by the thousand for no reason...
just sayin'... just sayin'
or you could try sticking some templates on some monsters and let him figure out what template you've added and what powers it gives the monster he's against...