Oh, I'm sure that being in a cold environment and letting it passively cool you is more efficient!

What I'm more unclear on is how small the impact is. It seems very likely to me that throwing the waste heat into the bottom of the ocean has less of an environmental impact than running A/C to suck out the heat and dump it into the air.

However, is the impact really so small that you wouldn't notice it just meters away? That's the part I'm unclear on.