I was curious about how this would actually work, were they using the equivalent of a desktop water-cooling rig (heatsink on CPUs with water flowing through to a radiator) or something else.  Reading the article, it's something else.

Essentially, they've got radiators on the backsides of the server racks, with fans to pull the air over the servers and through the radiators.  Not as efficient as having the heatsink on the processor, but does have the advantage of sucking up the waste heat from other components on the servers (FETs, NICs, etc.)

The big question is, is the total cost of something like this, including the installation, cheaper (both up front and over time) than a typical land-bound data center of equivalent size?  And, as others have pointed out, the warm water *will* attract sea life to the outflow, potentially blocking it, and the inflow has a chance of clogging up from pulling in debris and sea life.  Presumably they've got a screen to prevent such material from actually getting pulled into the system itself (or at least objects over a certain size,) but even so, eventually that screen is going to get covered...