Radiation is an even bigger problem, especially in the polar orbits they are talking about.

It’s only a problem if you get the machines up there! Which I’d argue is economically unviable to boot.

I don't think it was a stunt. It was an experiment.

I think passive cooling (running hot) reduced some of the advantages of undersea compute.

Ironically a benefit of underwater datacenters would be reduced cosmic rays. Not so great in orbit, I imagine!

I was listening to a Darknet Diaries episode where Maxie Reynolds seems to make it work: https://subseacloud.com/ I don't know how profitable they are, and I doubt this is scalable enough, but it can work as a business.

What about a data centre only running SQLite?

Well the thing is that it seemed to have been successful beyond all expectations despite being that? They had fewer failures due to the controlled atmosphere, great cooling that took no extra power, and low latency due to being close to offshore backbones. And I presume you don't really need to pay for the land you're using cause it's not really on land. Can one buy water?

Space is pretty ridicolous, but underwater might genuinely be a good fit in certain areas.

Hot saltwater is the worst substance on earth, excepting, maybe, hydrofluoric acid. You really don't want to cool things with ocean water over an extended period of time. And filtering/purifying it takes vast amounts of power (e.g. reverse osmosis).

My 4 Cylinder Diesel Volvo Penta is cooled by sea water. There is an elbow that may have to be replaced every few years,

I wonder why they did not start with a freshwater body.

I thought they had an issue with stuff growing on the cooling grates. Life likes to find warm water.

If it was successful beyond all expectations, why aren't we seeing more?

That's the question I was leading to, yes. Maybe the upfront cost for the unit of volume is simply too much.