Comment by inigyou

Yes, but that's localized and temporary. It's nothing like the ecological impact of burning fossil fuels, and more like the ecological impact of a quarry. It's a lower impact than a hydro dam, I think.

You have an intake that can suck in sea life accidentally, and an outlet that emits water too salty for sea life to survive, which doesn't go beyond a certain distance as it mixes again with normal ocean water.