Key Largo

Overview

Key Largo is the first and largest of the Florida Keys, running some 50 kilometres south-west from the mainland along the Overseas Highway. It is billed as the diving capital of the world, and that description is accurate in a way that shapes everything about a visit: the attraction here is offshore rather than at the waterline.

John Pennekamp Coral Reef State Park, the first undersea park in the United States, sits at the northern end and protects the reef tract lying a few miles out. Dive and snorkel operators work from marinas along the highway, and most visitors spend their time on a boat rather than on sand.

Natural sand beaches are few and small. Harry Harris County Park at Tavernier, at the southern end, has one of the better ones, and the state park has small swimming areas, but anyone arriving expecting a Florida strand should recalibrate. The shoreline here is mangrove, rock and shallow flats.

Our current condition score for this beach is .

Photo summary of last month

The pattern across the Keys is thick accumulation along a narrow waterline rather than weed spread thinly across a wide beach. That is a consequence of the shallow, still water here, and it means a modest arrival looks worse than the same volume would on an open Atlantic strand.

Position relative to the Atlantic sargassum belt

The Keys sit directly in the path sargassum takes out of the Caribbean. Weed carried west across the tropical Atlantic enters the Caribbean, tracks past the Yucatán, and turns north through the Florida Straits in the Florida Current, which runs immediately south of the island chain before becoming the Gulf Stream along the mainland coast.

Key Largo is at the northern end of that chain, closer to the mainland than Key West and slightly further from the strongest part of the flow, which is part of why it reads a little better than the Lower Keys in our data. It is still squarely on the route rather than off it.

Three local features make accumulation worse here than the same volume of weed would cause on an open beach. The water is very shallow for a long way out, so rafts ground close inshore. There is almost no wave energy to break weed up or take it back out. And the seagrass beds and mangrove fringe hold floating material rather than letting it pass.

The reef offshore is the fourth factor, and it works both ways. It intercepts a good deal of what is coming, which is why the dive sites can be affected while the shore is not, and the reverse is equally true. A report of clear water on the reef says little about the shoreline.

The sargassum season

In the Keys the season runs from roughly late spring into late summer, with the heaviest arrivals usually between May and August and little through the winter. Because arrivals here accumulate rather than clear, the practical difference between a good and a bad visit is measured in days, and it is worth checking the dated record immediately before travelling.

The Florida picture in full, including how the season has changed, is set out in our Florida sargassum season guide.

Swimming conditions and safety

The swim here is shallow and calm, with no surf to speak of, over a bottom of sand, seagrass and rock. Water shoes are genuinely useful rather than optional, and grass beds hide urchins.

The real hazards are boats rather than water. This is one of the busiest recreational boating corridors in the United States, with dive boats, fishing craft and channel traffic working constantly. Swim inside marked areas, and if snorkelling from a boat use a dive flag.

Lifeguard cover is limited to a few park beaches during posted hours; most of the shoreline has none.

On sargassum: fresh weed in the water is harmless. The strong sulphurous smell this shoreline can develop comes from thick material decomposing on hot sand and rock over several days and releasing hydrogen sulphide. Where mats have been sitting, walk around them rather than through them, since small stinging organisms live in the weed.

Choosing a hotel on this stretch

Accommodation on Key Largo runs along the Overseas Highway: dive lodges, mid-range hotels, a few resorts with their own small beaches, and vacation rentals on the canals. Almost none of it is on a natural sand beach, because there is very little natural sand beach to be on.

The question to ask a property here is not about the beach but about the water access: whether it has a dock, a swimming area, or a boat ramp, since that is how the Keys are actually used. Properties with their own maintained sand tend to clear it, which matters during the season.

Visitors whose priority is a beach rather than a reef should look at Bahia Honda State Park further down the chain, which has the best natural beach in the Keys and reads differently from Key Largo in our data.

Access and parking coordinates

Key Largo is reached by the Overseas Highway from Homestead and Florida City, around an hour from Miami. There is no rail service and public transport is minimal, so a car is effectively necessary. Miami International Airport is around ninety minutes by road.

Check live conditions before you go

The Keys accumulate what arrives rather than passing it on, so conditions here change over days and clear slowly. On the live map we track Key Largo with dated photographs and a current condition score, so you can compare it against Islamorada, Marathon and Key West on the same morning.