Swimming pool and the lobster effect
The problem is that you have umpteen megawatts of power coming out of your data centre at 40-50C you cool this with sea water at 2-3C.
Once the water you have heated gets to the output temperature of your data centre then you don't have any cooling anymore.
You can use a heat pump to boost the output temperature of the waste heat so you can use it to generate much hotter water. But boiling kids in the local swimming pool is the sort of publicity that even Google would have difficulty putting a positive spin on.
Or you could have a bunch of chillers to then cool the swimming pool to keep it habitable - but that rather ruins the whole point of the sea water system.
They probably do divert some of the heat to heat the rest of the building and, being Finland, probably a sauna or two.