Jules’ Undersea Lodge -- Key Largo, FL
Formerly the La Chalupa Research Laboratory, used in the '70s to explore the continental shelf, it's now one of Florida’s kitschiest attractions (and that's saying something). The only way to access the 600sqft, two-bedroom guesthouse is by scuba diving to its wet-room hatch.
Depth: 30ft
Rate: The $800 "JUL for Two" package covers a night's stay, and includes pizza delivery. We're not even making that up.
Most exotic fish that'll stare disapprovingly at you through the glass: Let’s just say you'd best start learning the words to “Barra-barracuda!”.