Not many full time live aboards in Belize
, if you exclude seasonal cruisers.
I used to live aboard at Roberts Grove in Placencia. One other live aboard there at the time. Used to be one at Chabli Mar, also in Placencia. Friends of mine used to live aboard at Cucumber Beach Marina in Belize City. To my knowledge, the total live aboard count hasn't changed much.
Most cruisers congregate in Placencia and to a lesser degree in Caye Caulker or Ambergris.
Where do you plan to be in Belize?