A Dubai-based developer has filed with the City of Sarasota for what may be one of the region's most unconventional luxury housing proposals yet: Poseidon's Retreat, an eight-unit Sarasota underwater condominium planned for Sarasota Bay. The proposal calls for eight luxury residences inside a transparent domed structure below the bay near downtown Sarasota. Plans describe terraced layouts, expansive glass walls, private observation lounges, climate-controlled marine gardens,