Rare Florida Keys mixed-use development opportunity with approx. 124,300 sq. ft. of uplands plus additional bay bottom ownership. Property includes 4 verified building rights with Letter of Site Condition on file. Existing improvements include a duplex and single-family home. Mixed Use (MU) zoning allows for a wide range of future possibilities, including commercial, residential, storage facility, marina-related use, workforce housing, market-rate housing, or potential subdivision into multiple parcels. Current zoning allows up to 6 market-rate units per acre or up to 15 affordable units per acre, buyer to verify per City of Marathon. The property offers approximately 216 feet of highway frontage, plus additional east-side access through an access easement, creating multiple entry points and flexibility for future site planning. A neighboring gas station adds convenience and commercial synergy for future development concepts. A unique feature is the sleeper asset of this property which is ownership/control of bay bottom extending behind approximately 12 lots along Cocoplum Drive, creating potential value tied to dockage, marina concepts, water access, assemblage opportunities, or long-term redevelopment. Deep-water access, good depth, multiple boating configurations, and proximity to the marked channel entrance add to the site's appeal. Large mixed-use tracts with water access and verified building rights are increasingly rare in the Florida Keys, making this a strong opportunity for an investor, developer, marina operator, or long-term land holder. Seller states property will be delivered vacant and free of personal belongings before closing. Buyer to verify zoning, density, building rights, permitted uses, dockage, water depth, access easements, permitting, and development potential.