Sargassum in the Cayman Islands: where to swim today, beach by beach

Live answer: today’s situation in the Cayman Islands is shown beach by beach on the map and in the list above, reassessed every morning from the official bulletins. Green dots (score 0-1) mark the quiet beaches, yellow or orange (2-3) a moderate presence that is still fine for a swim, red or black (4-5) the landings to avoid. On most days several beaches sit in the green even when others are loaded, and in Cayman the west coast is very often among them. Bear in mind that the picture can turn in 24 to 48 hours with the wind and the currents: a beach that is clear this morning can take seaweed tomorrow. So rather than memorising “that beach is good”, the reliable move is to check the day’s score shortly before heading out.

Sargassum is a floating brown seaweed (genus Sargassum) that drifts in huge mats across the sea surface. The phenomenon has escalated in recent years: carried by the currents of the tropical Atlantic, these mats cross the ocean from a wide belt between Africa and Brazil before reaching Caribbean shores, in the Cayman Islands as elsewhere. Out at sea the mats are useful, sheltering fish, turtles and crabs. The trouble is mass landings: piled on the sand, the seaweed rots within two or three days and releases strong-smelling gases. It is a natural process, but at a scale with no precedent, now tracked closely by scientific bodies and by the Cayman Islands authorities.

The mats ride the westbound currents of the tropical Atlantic and the trade winds, which blow out of the east, so Grand Cayman meets the flow with its eastern tip. Colliers Beach, in East End, opens due east and sits right in the regional stream; round the corner, the south coast takes the same flow a step behind, with Spotts Beach facing due south and Smith Cove (Smith Barcadere), a small southwest-facing cove at the corner of George Town, usually a notch below Spotts. The pattern is well documented: during the record regional influx of 2025, the local press described thick mats arriving in East End from mid-May before spreading along the south coast.

Exposed is not the same as closed, though. Outside a heavy landing these shores are perfectly usable, beach clean-up is overseen by the Department of Environment (with extra care during turtle-nesting season), and the day’s score has the last word.

Seven Mile Beach runs along the west coast of Grand Cayman, in other words the side facing away from the incoming flow, in the lee of the island. Seven Mile Public Beach and Governor’s Beach look due west, Cemetery Beach, towards the northern end of the strip in West Bay, faces southwest: to reach them, the mats would have to wrap around the whole island, and most strand on the exposed shores or drift past offshore long before that. The local press has drawn the same contrast year after year: even during the heavy 2025 season, while East End and the south coast were taking thick arrivals, Seven Mile Beach stayed clear. That is what makes the west the archipelago’s structural fallback, the stretch that usually stays swimmable when the east is loaded.

Structural does not mean guaranteed: an unusual spell of westerly wind can still push a batch into the bay, and the day’s score always has the last word.

The north of Grand Cayman lives at two speeds. The outer, reef-fringed shore, where Cayman Kai faces northeast, only really takes seaweed when the flow carries a north or northeast component, and the barrier reef blunts much of what gets through. Rum Point and Starfish Point look onto the North Sound, the wide, enclosed lagoon at the heart of the island: facing northwest and west respectively, they usually sit one or two notches below the outer reef coast.

Sheltered does not mean immune, though: in July 2022 an unusual amount of sargassum built up inside the North Sound itself, enough for the government to trial pumping the seaweed straight out of the water. Episodes like that are rare, but they are why even the lagoon beaches get a fresh score every morning.

The two Sister Islands lie around 130 kilometres northeast of Grand Cayman and meet the same east-to-southeast flow head on. On Cayman Brac, the Public Beach on the south shore opens southeast; on Little Cayman, Point of Sand, at the island’s eastern tip, looks due east. Both therefore move with the regional flow rather than with Grand Cayman’s day-to-day detail, and when the 2025 influx reached the archipelago the Sister Islands took arrivals along with Grand Cayman’s east coast. Local reports are scarcer there than on the main island, so satellite detection of the offshore mats carries more of the weight in their daily score.

The season mainly runs from March to October, often peaking between April and August, but it varies a lot from one year to the next. Some years bring almost nothing to the Cayman Islands, others, like 2025, set regional records. A landing lasts from a few days to several weeks, with no guaranteed end date: everything depends on the mats drifting in from the tropical Atlantic, on the currents and on the wind direction. In practice there are calm windows in the middle of the season, and an arrival remains possible outside it. That is why a daily update, beach by beach, is worth far more than a seasonal average when you are deciding where to swim.

In the great majority of cases, no: a beach with light or moderate sargassum poses no risk for swimming in the Cayman Islands. The risk comes with heavy, prolonged landings. As it decomposes, the seaweed releases hydrogen sulphide (H₂S) and ammonia, which smell of rotten eggs. In high concentrations these gases can bother sensitive people, such as asthmatics, babies and pregnant women, and they tarnish jewellery and electronics. Authorities close the worst affected spots (black score). For a visitor the rule is simple: as long as the smell stays faint and the score is below red, the beach is fine to use. That is exactly what the odour index shown on each beach summarises.

Partly, yes. The forecast rests first on satellite monitoring of the offshore mats: imagery picks them up tens of kilometres out, which opens a window of a few days depending on the currents and the trade winds around the Cayman Islands. The local authorities work the same way: the Department of Environment and the Cayman Islands National Weather Service follow the regional tracking and forecasting tools, NOAA’s among them. Over a longer horizon, monthly bulletins (NOAA, University of South Florida) estimate how much seaweed is sitting in the Atlantic, and therefore the risk over the coming weeks. FanGass combines those satellite outlooks with the official weather bulletins to anticipate, beach by beach, where a landing is likely. Since no forecast is fully reliable, as a change of wind can rewrite everything overnight, the daily update is what really makes the difference.

Every monitored beach in the Cayman Islands gets a score from 0 to 5 and a colour. Green (0-1): quiet, go ahead. Yellow (2): a little sargassum, swimming is fine. Orange (3): a moderate, visible amount, but you can still swim; plenty of people do, and you decide based on the smell that day. Red (4): heavy landing, strong smell, better to avoid. Black (5): evacuated zone. The rule worth remembering: only red and black are genuinely to be avoided, and below that swimming remains possible. An odour index (none / faint / strong) completes the score, because it is often the smell of decomposition, more than the seaweed itself, that ruins the outing.

There is no need to cancel a holiday in the Cayman Islands: the islands’ geography works in your favour. The west coast, from Seven Mile Public Beach to Governor’s Beach and Cemetery Beach, sits in the lee of the island and stays clear on the vast majority of days, and the North Sound lagoon (Rum Point, Starfish Point) is usually quiet too. Even the exposed shores, Colliers Beach, Spotts Beach or Smith Cove, are perfectly pleasant outside a heavy landing, and most beaches stay swimmable with light to moderate sargassum. The best move stays the same: check the day’s score, beach by beach, and let the map pick the side of the island for you.

Every morning, FanGass gathers the official monitoring sources (the Department of Environment, the Cayman Islands National Weather Service, NOAA AOML, the University of South Florida monthly outlook and the local press, Cayman Compass first among them), cross-checks them against satellite imagery of the offshore mats, and boils it down to a score from 0 to 5 per beach in the Cayman Islands. User reports from the ground adjust the scores live when several agree, and everything is reassessed each day. The service is free, edited by the Katchak agency.