Sargassum in Puerto Rico: where to swim today, beach by beach

Live answer: today’s status in Puerto Rico 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, largely because the island has shorelines facing every direction. Be aware: conditions can flip within 24 to 48 hours depending on wind and currents, and 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 surged in the early 2010s: pushed by tropical Atlantic currents, it crosses the ocean from a vast belt between Africa and Brazil before washing ashore in the Caribbean, in Puerto Rico as elsewhere. Out at sea it is useful, sheltering 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 is a natural process, but on an unprecedented recent scale, now closely tracked by scientific agencies and local authorities.

Landings mainly hit the east coast and the southeast coast, facing the open Atlantic and the trade winds: the rafts crossing the ocean reach those shores first, and the wind pins them against the sand rather than carrying them away. On the east coast, Playa La Pared and Balneario La Monserrate (Luquillo), Balneario Seven Seas (Fajardo) and Playa Los Machos (Ceiba, facing the Vieques passage) are the most exposed spots. In the southeast, Balneario Punta Santiago (Humacao), Playa Guayanés (Yabucoa), Playa Punta Tuna (Maunabo), Balneario de Patillas and Balneario Punta Guilarte (Arroyo) get frequent landings, and the seaweed tends to get trapped in the enclosed coves.

The north-facing San Juan strip (Balneario El Escambrón, Playa del Condado, Ocean Park, Isla Verde, Balneario de Carolina, Pocita de Piñones) sits in between: it faces north, gets far less than the east coast, and the public beaches are raked regularly.

But "affected" doesn’t mean "off-limits": outside a heavy landing, these beaches are swimmable on many days. The day’s per-beach score is the only real judge.

Vieques and Culebra lie further east than the main island, so they sit first in the path of the rafts, and their north and east shores take the most: Playa Flamenco and Playa Zoní (Culebra) face north and northeast, right in the line of the trade wind. On Vieques, the south coast faces the Caribbean and is usually better sheltered: Sun Bay, Media Luna, Playa Caracas and La Chiva sit behind the island’s ridge, though sargassum can still work its way round during a big landing.

One practical detail: these are barely developed beaches with little or no mechanical cleaning, so the seaweed stays on the sand longer than at a San Juan public beach. Check the day’s score before booking the ferry or the flight from Ceiba.

The west coast is the island’s big fallback: Playa Domes (Rincón), Balneario Crash Boat (Aguadilla), Playa Buyé and Balneario de Boquerón (Cabo Rojo) sit in the lee, with their backs to the trade winds and the whole island between them and the sargassum flow. Landings there are much rarer and usually light.

The southwest and the south coast work much the same way, shielded by the central mountain range: Playa Sucia (Cabo Rojo), Playa Santa and Balneario Caña Gorda (Guánica), Playa Rosada at La Parguera (Lajas) and Playa El Tuque (Ponce) face the Caribbean and are usually calm, though a landing that wraps around the southeast tip can reach them.

That said, you don’t have to chase "zero sargassum": a beach with light or moderate seaweed is perfectly swimmable. Confirm on the map on the day.

The season mainly runs from March to October, often peaking between April and August, but it varies a lot from year to year in Puerto Rico. 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, especially along the east coast. 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 in Puerto Rico. 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 such as asthmatics, infants and pregnant women, and tarnish jewellery and electronics. Authorities close or 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 in Puerto Rico. Because the trade wind pushes from the east, what shows up east of Culebra usually foreshadows what reaches Fajardo and Humacao. 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. Since no forecast is 100 % reliable, as the wind can change everything overnight, it’s the daily update that makes the difference.

Each monitored beach in Puerto Rico 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 and it’s 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 Puerto Rico: the island has shorelines facing every direction, so there’s almost always a swimmable beach within an hour’s drive. If you’re worried, the west (Rincón, Aguadilla, Cabo Rojo) and the southwest are the calmest, and the north-facing San Juan strip is a solid middle ground. There’s no need to write off Luquillo, Fajardo or Vieques outright either, since they’re fine on many days and the public beaches clean the sand. Best move: check the day’s per-beach score, and keep the west coast as your plan B.

Every morning, FanGass aggregates the official monitoring bulletins (DRNA, the Puerto Rico Sea Grant Program, NOAA AOML, 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 in Puerto Rico. 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.