My bet is this could be for DR data centers to isolate them from possible land based disasters, fire, flood, earthquake etc. Tsunami coming, power up and head for deep water. Flood, well, its a ship and it floats! Virus/zombie pandemic, improved quarantine and isolation.
I just want to know what they use for the data hookup - satellite links I would think would have far too much lag, and bee too slow for serving data, so unless these are just used to store backups and critical operations stuff, it is hard to see the advantages, especially as in the US at least you can still rent/buy old missile silos or fallout shelters to give you a nice stable environment for a server farm.