Sargassum in Cancún & the Riviera Maya: where to swim today, beach by beach

Live answer: today's status on the Mexican Caribbean coast is shown beach by beach on the map and list above, re-assessed every morning from the official bulletins. Green dots (score 0-1) mark the clear beaches, yellow or orange (2-3) a moderate but swimmable amount, red or black (4-5) the landings to avoid. On most days several beaches are green even when others are loaded. Be aware: conditions can flip within 24 to 48 hours depending on wind and currents — a clean beach this morning can get a landing tomorrow. So the reliable habit isn't to memorise "this beach is good", but to re-check the day's score right before you head out.

Sargassum is a floating brown seaweed (genus Sargassum) that drifts in huge rafts across the sea. The phenomenon has surged since 2011: pushed by tropical Atlantic currents, it crosses the ocean from a vast belt between Africa and Brazil before washing ashore in the Caribbean, on the Mexican Caribbean coast as elsewhere. Out at sea it is useful — it shelters fish, turtles and crabs. The problem is the massive landings: piling up on the shore, the seaweed rots within two or three days and releases foul-smelling gases. It's a natural process, but on an unprecedented recent scale, now closely tracked by scientific agencies and local authorities.

Strandings mostly hit the east-facing mainland coast: Playa del Carmen (Mamitas, Fundadores, Playacar), Puerto Morelos, Akumal, Xpu-Há and Tulum (Paraíso, Pescadores, the Ruins beach) — the Cozumel channel dumps there the sargassum that piles up south of the island. In Cancún, the hotel zone’s east façade (Chac Mool, Marlin, Ballenas, Delfines) takes the regional flow, and the Costa Maya (Mahahual) sometimes takes even more, as the first landfall of the branch coming up from the south.

But “affected” doesn’t mean “off-limits”: outside heavy strandings, Playa del Carmen and Cancún stay swimmable most days — and resorts rake the sand every morning. The daily per-beach score is the only real judge.

The Mexican Caribbean has three structural refuges: Cozumel’s west coast (San Francisco, Palancar), sheltered by the island itself even when its east coast saturates; the Bahía de Mujeres — Playa Norte on Isla Mujeres, Playa Mujeres / Costa Mujeres and Cancún’s north-facing beaches (Langosta, Tortugas, Caracol) — tucked behind the elbow of Punta Cancún; and Holbox, facing the Gulf of Mexico, outside the sargassum belt’s track.

That said, you don’t need “zero sargassum”: a beach with light or moderate sargassum is perfectly swimmable. Just confirm it on the map the same day.

The season mainly runs from March to October, often peaking between April and August — but it varies a lot from year to year on the Mexican Caribbean coast. Some years are nearly spared, others break records. A landing lasts from a few days to several weeks, and there's no guaranteed end date: it all depends on the rafts drifting in from the tropical Atlantic, the currents and the wind direction. In practice, there are calm windows even at peak season, and a landing is still possible off-season. That's why a daily, beach-by-beach update is far more reliable than a seasonal average for deciding where to swim.

In the vast majority of cases, no: a beach with light or moderate sargassum poses no risk for a swim on the Mexican Caribbean coast. The risk appears during heavy, prolonged landings: as it decomposes, the seaweed releases hydrogen sulfide (H₂S) and ammonia, a rotten-egg smell. At high concentration these gases can bother sensitive people — asthmatics, infants, pregnant women — and tarnish jewellery and electronics. Authorities evacuate the most exposed spots (black score). For visitors the rule is simple: as long as the smell stays faint and the score is below red, the beach is fine. That's exactly what the smell index shown for each beach captures.

Partly, yes. Forecasting rests first on satellite monitoring of the offshore rafts: imagery spots the mats tens of kilometres from shore, giving a window of a few days depending on currents and trade winds on the Mexican Caribbean coast. Longer term, monthly bulletins (NOAA, University of South Florida) estimate how much seaweed is in the Atlantic, and thus the risk for the coming weeks. FanGass combines these satellite forecasts with the official weather bulletins to anticipate, beach by beach, where a landing is likely. As no forecast is 100 % reliable — the wind can change everything overnight — it's the daily update that makes the difference.

Each monitored beach on the Mexican Caribbean coast gets a 0-to-5 score and a color. Green (0-1): clear, go for it. Yellow (2): some seaweed, perfectly swimmable. Orange (3): a moderate, visible amount, but still swimmable — plenty of people go in, your call depending on the day's smell. Red (4): heavy landing, it stinks, skip it. Black (5): evacuated zone. The rule to remember: only red and black are really to avoid; below that, a swim is fine. A smell index (none / light / strong) completes the score, because it's often the rotting smell, more than the seaweed itself, that ruins the outing.

No need to cancel a holiday in Cancún or the Riviera Maya: there is almost always a swimmable beach, and most stay enjoyable even with light to moderate sargassum. If you’re worried, Isla Mujeres (Playa Norte), Cozumel’s west coast and Holbox are near-safe bets; but don’t write off Playa del Carmen or Tulum upfront — many days are fine and the resorts clean the sand at dawn. Best move: check the daily score, beach by beach.

Every morning, FanGass aggregates the official monitoring bulletins (NOAA satellite monitoring, the Quintana Roo sargassum monitoring network, the University of South Florida monthly outlook and local press), cross-checks them against satellite imagery of the offshore rafts, then distills it all into a 0-to-5 score per beach on the Mexican Caribbean coast. On-the-ground user reports adjust the scores live when several agree, and everything is re-assessed daily. The service is free, published by the Katchak agency.