How about a Granny House Boat, you could advertise water views
Seriously, I often wondered about a GF where a pool is. The cost to reclaim the pool can add up, but perhaps it could become part of the GF such as a basement or storeroom. Much engineering to consider.
Agree with others, not a good GF site. Access would be via the narrow sides so very little privacy. What about the area? It is it a family area in need of a back yard and pool? If yes, the rental prospects for the front house just dropped and your total yield may well not be worth the effort.