ShipStead
This page should be filled out with the arguments in favor of using a Cruise Ship as a Seastead condo (maybe some against too).
Arguments In Favor
You can buy used cruise ships for reasonable amounts of money. These could then be sold off as condos at reasonable prices. This could be a lower risk way to get an ocean safe seastead going. See also Patri's ShipStead project page. Jeff Chan prefers the term "CondoStead" since a condo/timeshare is a familiar concept, easier to sell and explain, etc.