Where is this confusion coming from? Are you suggesting there won't be colder water around the data centre? Or just nitpicking for the sake of it?

It looks like my original comment hit some HN ideological hot spot (unintentionally), but it's entirely uncontroversial scientifically.

> Where is this confusion coming from? Are you suggesting there won't be colder water around the data centre?

If a fish is swimming in 24°C water, it can't simultaneously be swimming in 19°C water. Maybe its friend 10 meters away is swimming in 19°C water, but that doesn't help the first fish.

Maybe that fish feels more comfortable in 24°C water, because it needs a certain body temperature to keep its internal processes running (i.e., to not freeze to death), but it cannot harvest energy from the 24°C water, which is what you claimed above. I'm not nitpicking, this is one of the most fundamental and important laws of physics.

I don't know whether this is feasible at the temperature gradients created by data centers, but it's not prohibited by physics. If there are chemical species in the water that are stable at 24 C and not 19 C, the fish can harvest these for chemical energy after they have traveled the ten meters.

This is probably more relevant at temperature gradients greater than 5C, but it's thermodynamically possible.