There are a number of 6-8GWe nuclear plants that dump 15+GW into the nearby sea (or in the case of Bruce, into Lake Huron). I don't see it being much of an issue. Better than virtually any other cooling option.

The issues are maintenance, energy source, and equipment supply.

Good point, although on the local scale you mention, wildlife could still be impacted. Hopefully, the overall impact on the ecosystem will be monitored and studied before expanding these data centers more broadly.

I don't think people mean literally boil the ocean. Just increasing it by few Celsius degrees can be world ending.

That's a good point. Maybe not cool, but it would warm the water less.
(I'm guessing solar cells reflect less energy back into space than water, since they're specifically designed not to.)

Most stressful job imaginable

The issue with climate change was never with "heat production". It's always been the generation of heat trapping chemicals. The sun sends a stupid amount of energy our way. Generally the earth radiates almost the same amount back out into space, with a minor amount captured by various things, like photosynthesis.

Pollution alters that equation and causes more energy from the sun to get trapped in the atmosphere. That's the problem. We could never generate as much energy as the sun (even the tiny amount that hits the earth), but we can definitely alter the atmosphere to trap more and more of that heat.

Also, the ocean is a MASSIVE heat sink. I saw someone work out the calculations recently, I don't remember the numbers, but the conclusion was that we'd never measure a notable increase in ocean temps if we housed every datacentre in existence in the ocean. The sun hitting the ocean every day dumps more energy into the ocean directly than we'd ever be able to manage.

It all comes down to pollution.

This page says the ocean is about 352,670,000,000,000,000,000 gallons, which is about 1.3 x 10^21 liters, and each liter is a kg of water (yeah, yeah, the dissolved salt adds some mass but I don't think it adds sufficient thermal mass to make a difference). It takes 4.184 kilojoules to raise 1kg of liquid water 1°C, and 1 joule is 2.778 x 10^-4 wh.

So that's 1.55 x 10^18 watt hours, or 1,550,000 TWh.

Global electricity consumption is about 30,000 TWh per year, so if you use the entire world's electricity consumption for 51 years you'd raise the oceans' temperature by 1°C.

Or if you take global data center power capacity of about 125 GW, and ran them at full power 24/7, you'd be producing about 10.8 TWh per day or 3944 TWh per year. It'd take about 393 years of the world's data centers to raise the ocean by 1°C.

Just goes to show that much more of the energy heating up our world and our oceans is coming from the sun heating up the planet and the planet failing to radiate it out past our greenhouse blanket, not from the actual heating of our atmosphere from our own energy sources.

Sure, if there is zero weather a building wouldn't be needed.

Saltwater is one of the harshest terrestrial environments for a data center other than maybe lava. Pressure, oxygen, and sodium ions make the ocean extremely corrosive to metal structures.

You could be right about the first part, but I take issue with the second. Ships in seawater usually need sacrificial anodes so corrosion eats those instead of the hull and fasteners. I'm not sure how that would affect heat exchange, maintenance, or long-term reliability. It would definitely limit the materials you could use.