The venomous clinging jellyfish is back in New Jersey's back bays. It is tiny, hard to see, and its sting can send people to the emergency room. This page maps where state and university crews have actually recorded it, drawn from 701 samples across 8 waterbodies between 2016 and 2026.
A record of past samples, current as of the 2026 season — not a live conditions report.
The clinging jellyfish (Gonionemus vertens) is about the size of a dime, roughly 1 inch across, and nearly transparent. It has more than 60 tentacles and carries a neurotoxin; stings can be painful and, for some people, cause symptoms beyond the skin. It is not the common sea nettle, and it is much smaller.
It lives in shallow estuaries and back bays, typically in water up to about 4 feet deep, where it clings to eelgrass and submerged vegetation. You are not going to meet one in the ocean surf — this is a back-bay and estuary animal, most often encountered in late spring and early summer, when back-bay water warms toward the low 80s°F.
Each point is one sample. Red means clinging jellyfish were counted; gray means a sample with none found; the faint points are samples logged without a count.
Clinging jellyfish are found here frequently in the monitoring record, sometimes in large numbers.
Clinging jellyfish turn up repeatedly across years of sampling here.
Clinging jellyfish have been recorded here, though not often.
Crews have sampled here without recording the species — but absence of records is not absence of jellyfish.
There are too few recorded counts here to describe how common clinging jellyfish are.
These are summaries of the sampling record, not live risk ratings. No location is labeled "safe" — absence of records is not absence of jellyfish.
Ocean County
Cape May County
Monmouth County
Ocean County
Ocean County
Areas with thinner or older records — Manasquan River, Central Barnegat Bay, Southern Barnegat Bay and LBI — are covered on the Monmouth County, Ocean County, Cape May County pages.
If you are stung, get out of the water and seek medical care. Reactions to a clinging jellyfish sting can be more severe than a common sea-nettle sting.
For treatment guidance call the NJ Poison Control Center at 1-800-222-1222, or seek emergency care for severe symptoms.
NJ Poison Control: 1-800-222-1222
Records come from NJDEP Bureau of GIS / Montclair State University — Clinging Jellyfish Monitoring. Each row is one sample observation; many were logged without a count, and those are reported separately rather than treated as zero. Areas are grouped from point samples, so boundaries are approximate. NJDEP data layer.
See also our general beach safety guide.
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