It's generally bad and kills local eco system with algae blooms and messing up seasonal cycles of nutrients/food. But that's just with dumping the heat into environment especially in freshwater river based reactors and a pretty raw system of dumping hot water into the river ...

Clever use of physics and cooling towers allows us to mitigate the problem..release the energy slowly over time or use the thermal for something else.but costs a lot more than just dumping it into ocean and doing lazy misleading napkin math.

Yes of course, local impacts would be more pronounced. Wouldn’t want them near coral or anything.

To be clear, this isn’t an argument for underwater DCs. I just think it’s important to keep the scales of these things in view, so one doesn’t dilute actual causes of large scale climate change (GHGs etc.) with things like this that have basically zero chance of any even mesoscale effect.

I am starting to be convinced that anything we do (at scale, over time) will become "counter-environmental" ...

... it is as if the only thing that suits our poor planet is some sort of very delicate homeostasis, which we disrupt, in what amounts to, our fight against entropy.-