Sargassum at Trunk Bay (St John): today's conditions
Clear
Easy, go
Trunk Bay is the postcard of St John: a crescent of brilliant white sand inside the national park that covers much of the island, complete with its well-known marked snorkel trail just offshore.
To enjoy it without a letdown, this page follows sargassum day by day. The bay's score, from 0 to 5, comes out of the morning satellite pass, while the map takes in the whole north shore of St John at once.
Trunk Bay on the sargassum map
What to know about this beach
Opening to the north-west, Trunk Bay belongs to the string of sheltered inlets along St John's north coast, with Cinnamon Bay and Maho Bay continuing the line to the east. The trades sweep the archipelago from east to west and strike the island's eastern face first; here, the wooded ridges of the park act as a buffer and the bay stays out of the main flow for most of the year.
Exceptions happen: weed sliding past the island's northern points can dust the bay, and the rocks dividing the shore into small coves sometimes trap strands where the sand next door stays spotless. Nothing, however, on the scale of what the windward coasts go through.
Frequently asked questions
Is the snorkel trail usable when sargassum is around?
With a low score, yes: the bay keeps its clarity. As the score rises, surface strands can cloud the water above the trail, so a glance at the morning reading saves a wasted trip.
Is Trunk Bay better off than Cinnamon Bay or Maho Bay?
All three share the shelter of St John's north-west coast. Differences come down to detail: the day's current, rocky points, the shape of each cove. The sector map settles the question.
Does the east side of St John get more sargassum?
Yes: that face meets the flow driven by the trades and logs arrivals first. The north shore, Trunk Bay included, lives clear of most of the traffic.
When should I watch more closely?
Mainly from spring to late summer, when mats cross the archipelago in numbers. Outside that stretch, the bay posts low scores most of the time.