The Overseas Highway traces 113 miles of open water and forty-three bridges, but long before U.S. Route 1 stitched the archipelago together in 1938, the only passage to the Keys was by boat. Maritime commerce defined the region for three centuries: wreckers salvaged ships torn apart on coral reefs, sponge divers harvested Tarpon Basin floors, and cigar runners ferried Cuban tobacco through mangrove channels the Coast Guard could not navigate. Today that legacy persists in departure schedules posted at Bayside Marketplace, where every Florida Keys boat tour from Miami begins at the same numbered slips once reserved for mail packets and freight schooners. Biscayne Bay serves as the natural threshold. Its shallow turquoise flats stretch sixteen miles south from downtown Miami, protected by a barrier reef system older than the Everglades themselves. Tour vessels crossing these waters pass Stiltsville, a skeletal village of seven plank houses built on pilings in the 1930s by fishermen who wanted to escape Prohibition enforcement on land. Beyond the bay mouth lies the Atlantic shipping lane, where container traffic from the Port of Miami shares the horizon with sport-fishing charters bound for the Gulf Stream. The transition from urban waterfront to open ocean takes forty minutes by modern hull design, but the shift in water color—from harbor green to cobalt—marks the exact line where Florida's continental shelf drops away. Key West itself rests ninety nautical miles southwest of Miami, a distance that for day-trippers translates to four hours aboard high-speed catamarans departing at dawn. The intervening islands—Key Largo, Islamorada, Marathon—each claim distinct ecological niches. John Pennekamp Coral Reef State Park, the first underwater preserve in the United States, protects seventy nautical square miles of elkhorn coral and brain coral formations that survived the 1998 bleaching event. Charter operators running snorkel excursions here follow strict mooring protocols; anchors are forbidden within park boundaries. Further south, the Bahia Honda Channel funnels tidal currents strong enough to require local pilotage knowledge, a holdover from the days when navigating these passes without charts meant reading current direction from the lean of channel markers. The boat tour infrastructure operating from Miami today reflects both recreational demand and environmental regulation. Vessels must comply with manatee speed zones in Biscayne Bay year-round, and seasonal turtle nesting closures restrict beach landings on certain outer keys from May through October. Operators scheduling Florida Keys boat tour from Miami departures balance these constraints against tide tables and the predictable afternoon thunderstorm pattern that builds over the Everglades between June and September. Morning launches remain standard practice, not for marketing appeal but because wind speed doubles by two o'clock, turning flat bay crossings into forty-minute slogs against three-foot chop.