Ever seen China Syndrome, or maybe an episode of Captain Planet? Putting aside all the toxins in fresh-and-seawater that are hazardous to life and limb, water runoff from nuclear reactors and the treatment thereof is a big issue for power plants...
If you're almost willing to go with spirit-of-the-ocean-summoning powers, some radioactivity-triggered hydrokinesis would seem a reasonable move to consider, not to mention being very Classic Superhero. You could even put a modern, Michael Moore-ish spin on it, where the character has these fantastic powers because he got exposed to a LOT of the rads/toxins/waste all at once, but all these people who got exposed to it through the groundwater got sick and/or died, so this spurs him to use his powers to fight for truth and justice against a careless and corrupt world. Sort of Green Arrow-by-way-of-Matt Murdock, ish, kind of.
Maybe.
Namewise: Coriolis, Hellspont, Charybdis, Squall, White Squall, Roguewave, Surfside, Doctor Drench, H20, H20verdrive, Ripple, Current Event, Sea Leveler, Rapid, Niagara, The Sublimator, Fluid, Flow, Crest, Whitecap, Tributary, Reservoir, Downpour, Flashflood, Super Soaker, The Diver, Freestyle, Lifesaver, Lifeguard, High Tide, then you've got your sea creatures...Sea Snake, Scorpion Fish, et al.
