What is a clinging jellyfish?

The clinging jellyfish (Gonionemus vertens) is a small, nearly transparent jellyfish about the size of a dime, with more than 60 tentacles. It carries a neurotoxin, and its sting can be more severe than a common sea-nettle sting. It lives in shallow back bays and estuaries, clinging to eelgrass and submerged vegetation, not in the open surf.

Where in New Jersey are clinging jellyfish found?

Monitoring has recorded them most often in back-bay waters such as the Metedeconk River, the Shrewsbury and Navesink Rivers, the Cape May and Wildwood back bays, and parts of Barnegat Bay. They are a late-spring and early-summer animal in shallow, vegetated water up to about four feet deep.

Does this monitoring data tell me a beach is safe?

No. These are point-in-time sample observations, not a live hazard map, and many samples were logged without a count. The absence of a record does not mean clinging jellyfish are absent. Use the data as background and stay cautious around eelgrass in shallow back-bay water in early summer.

Clinging Jellyfish in Metedeconk River

Most active in the recordOcean County

Monitoring summary, current as of the 2026 season. This is a record of past samples, not a live conditions report.

No other waterbody in New Jersey's clinging jellyfish records shows up the way the Metedeconk River does. Crews working this river have logged the species in 102 samples since 2018, and one sample held as many as 351.

By the numbers

102

samples with clinging jellyfish

sampled, none found

sampled, no count recorded

157

total samples (2018–2026)

Largest single count: 351 · most recent detection: 2026

Here is the breakdown: 102 samples with clinging jellyfish, 7 sampled with none found, and 48 more where no count was recorded. We report the raw tallies rather than a percentage, because so many samples lack a count.

Year by year

'18

'19

'20

'21

'23

'24

'25

'26

jellyfish counted sampled, none found no count recordedSampling effort varies year to year, so bar height reflects how much crews sampled, not risk.

Across the years with enough samples to compare, the recorded detections have held fairly even. As always, this describes the sampling record rather than the underlying population.

When to be careful

Clinging jellyfish are largely a late-spring and early-summer animal here, showing up as back-bay water warms. The biggest single count in the Metedeconk River, 351, was recorded on June 12, 2018, which lands squarely in that window.

If you are swimming, paddling, or letting kids wade in the Metedeconk River in late spring or early summer, it is worth knowing this is the most documented spot in the state. The animal lives in shallow back-bay water and on eelgrass, not out in the surf, so caution belongs in the bays and lagoons, not on the ocean beaches.

Where these samples were taken

💧

Scroll to load jellyfish monitoring map

Sampler notes from the Metedeconk River also mention other jellyfish recorded along the way, such as Chrysaora chesapeakei (bay nettle), picked up incidentally during clinging jellyfish surveys rather than tracked in their own right.

What the clinging jellyfish is, and what to do if you are stung

The animal

About the size of a dime — roughly 1 inch across — and nearly transparent, so it is easy to miss.
Has more than 60 tentacles and carries a neurotoxin; stings can be painful and, for some people, cause symptoms beyond the skin.
Lives in shallow estuaries and back bays, typically in water up to about 4 feet deep, where it clings to eelgrass and submerged vegetation. It is not an open-surf animal.
This is not the common sea nettle; it is much smaller and its sting can hit harder.
In New Jersey it is most often encountered in late spring and early summer, when back-bay water warms toward the low 80s°F.

If you are stung

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

Towns nearby

Communities on or near the Metedeconk River include Brick and Point Pleasant, and each one has a full guide on the site.

brick
Point Pleasant Beach

How to read this page

A note on how to read this page. Each figure comes from individual sample observations collected by Montclair State University and the NJ Department of Environmental Protection between 2018 and 2026. A count reflects what a crew recorded at one spot on one day; many samples were logged without a count, and those are left out of the tallies rather than treated as zero. Areas are grouped from point samples, so boundaries are approximate. Most importantly, the absence of a record is not proof the species is absent. Data current as of the 2026 season.

Source: NJDEP Bureau of GIS / Montclair State University — Clinging Jellyfish Monitoring. NJDEP data layer.

Frequently asked

Have clinging jellyfish been found in the Metedeconk River?: Yes. Clinging jellyfish have been recorded in the Metedeconk River — 102 samples since 2018, most recently in 2026.
Where in the water are clinging jellyfish a concern?: They live in shallow estuaries and back bays, typically in water up to about four feet deep, where they cling to eelgrass and submerged vegetation. They are not found out in the ocean surf.

Other monitored waters

Beach safety updates

Get seasonal Jersey Shore beach and water alerts in your inbox.

No spam. Unsubscribe anytime.