The Ten Thousand Islands are not ten thousand. Surveyors have counted somewhere near five hundred, and the number shifts with every storm surge that redraws a sandbar. This is the largest mangrove estuary in North America, a lattice of red, black and white mangroves stitched across the Gulf edge of the Everglades. The archipelago began as oyster bars. Shell built up, mangrove seedlings caught hold, sediment gathered, and islands assembled themselves from the bottom up. Human occupation is older than the mapping. The Calusa raised shell mounds here for well over a thousand years, engineering canals and terraces from discarded oyster and whelk shells; Marco Island's own Key Marco site yielded carved wooden artefacts in 1896 that remain among the finest pre-Columbian objects found in North America. Later came plume hunters, clam dredgers and the small fishing settlement of Goodland, still the launching point for a ten thousand islands boat tour everglades departure at 750 Palm Point Dr. Protection arrived in 1996, when the Ten Thousand Islands National Wildlife Refuge was established across roughly 35,000 acres of mangrove forest, tidal creek and salt marsh. Entry to the refuge itself costs 0 USD; the water is public, and the operators who run Marco Island Everglades boat tours hold commercial permits to cross it. The refuge exists chiefly for what moves through it — West Indian manatees grazing on turtle grass, bottlenose dolphins working the tidal cuts, roseate spoonbills and wood storks feeding the shallows, and one of the densest populations of American alligators and crocodiles sharing overlapping range anywhere in the United States. The hydrology explains the abundance. Freshwater sheet flow drains south through Big Cypress and the sawgrass prairie, meets salt water at the mangrove fringe, and creates a brackish nursery where snook, tarpon and juvenile sharks mature. Mangrove roots trap sediment, buffer hurricane energy and store carbon at rates exceeding most terrestrial forests. Everglades National Park's boundary lies immediately south, making the refuge a functional corridor rather than an isolated preserve. What a visitor sees from a deck is therefore a working system, not scenery. Airboats reach the sawgrass interior; shallow-draft vessels thread the estuary; catamarans run offshore toward Cape Romano and its half-submerged dome houses, sinking gradually into the Gulf since 2005. The operators selling ten thousand islands boat tour everglades tickets — from Miami airboat runs to Naples cypress-walk combinations and dolphin-watching departures out of the islands themselves — each cover a different band of that gradient. The refuge remains open 07:00–20:00 daily, and the estuary continues doing what it has done for four thousand years: building land out of shell, root and tide.