New Jersey Scuba Diving



Moon Jelly - Aurelia aurita

The many creatures on this page are lumped together for the one trait they all have in common - they are all "jelly-like" - soft, gelatinous, and more-or-less transparent. Other than that, they are for the most part completely unrelated. True Jellyfishes, Hydromedusae, and Siphonophores are in the phylum Cnidaria, related to bottom-dwelling Hydroids, Sea Anemones and corals. Comb Jellies are in the phylum Ctenophora, and are completely unrelated to jellyfishes, as are Sea Butterflies and Corollas, which are mollusks. Salps are free-swimming tunicates, more closely related to us than to any of these other creatures. Squids are here only because I can't think of any better place to put them, and they are kind of squishy too.

Cnidarian lifecycle - in this case, a hydroid. Others are similar.

The actual stinging apparatus of a cnidarian is microscopic - specially developed cells.
That doesn't mean they can't hurt you !

Small harmless hydromedusae also appear sporadically in freshwater. There are also some types of freshwater jellyfish, but not around here. The rest of the ( non-cnidarian ) creatures on this page are unrelated, sharing only their drifting lifestyles.

Photos by Herb Segars
Text by Herb Segars &
Click images for more galleries !

True Jellyfishes


Jellyfishes are free-swimming relatives of corals, anemones, and hydroids. In fact, in many cases they are the same species, just in a different stage of life ! Not all medusas ( as jellyfishes are called ) have a corresponding polyp stage, and likewise not all polyps have a corresponding medusa stage, but most alternate generations in each form. Small jellies ( up to 1" across ) are most likely the medusa stage of some hydroid, while large jellies are usually the dominant stage of a species in which the polyp stage is almost absent. Even anemones have a periodic medusa stage, although it is infrequently observed.

Although jellyfish can swim slowly, they are largely at the mercy of the tides and currents, and at times large numbers are concentrated into bays, and may be stranded on beaches.

When jellyfish breed, they release tiny swimming embryos into the water, and the adults then probably die. The embryos attach themselves to fixed structures, and it would be well worth looking for them on the piles of piers, although they are only 1 or 2 cm long. They look a bit like tiny sea anemones for a long time, and feed and grow like this for a year, hanging downwards from a support. In their second winter they lose their tentacles, and their bodies elongate and gradually divide crosswise into a stack of little discs. Eventually these break free one by one and swim away to grow into tiny jellyfish.

Clinging Jellyfish Warning - 2016

Clinging Jellyfish - Gonionemus vertens
very dangerous

This is a Pacific coast jellyfish that has been spotted along the East Coast for many years, but until recently has been uncommon. It is slightly larger than a quarter, about one inch in diameter. The sting of this jellyfish will send you to the hospital, not just people that are especially sensitive, but anyone. It is found in bays and inlets where it clings to sea grasses, it is not normally found in the open ocean. Your best protection against jellyfish stings is an exposure suit, even a lycra skin is thick enough to block the microscopic stingers.

Moon Jelly - Aurelia aurita
Inside the top of the bell you can see four rounded masses, which are the gonads.

Translucent Moon Jellies are harmless and quite common. Red Jellies have a painful wasp-like sting, but are usually much less common. And try as you might to avoid it, sooner or later every northern diver will get a stray tentacle draped across the face and lips - the only places exposed to attack.

Moon Jellyfish do not sting humans. The threadlike tentacles around the edge of the bell can sting, and may occasionally catch small swimming animals for food, but their stings - like minute harpoons fired by springs - are not powerful enough to pierce our thick skin. They feed mostly by trapping microscopic plankton in a film of mucus which flows over the surface of the bell and is picked off as it reaches the edges by the thick mouth tentacles underneath. They swim by pulsing the bell, pushing themselves slowly forwards through the water.

Red or Lion's Mane Jellyfish - Cyanea capillata
Avoid these

The Red or Lion's Mane Jellyfish has a bell reaching up to eight feet in diameter, and tentacles longer than a blue whale - up to 200 feet long. Juveniles are pink, turning red as they mature, becoming brownish purple as adults. This jellyfish can cause severe stings, and there have been rare reports of fatalities to swimmers. In one of the Sherlock Holmes mysteries by Sir Arthur Conan Doyle, a Lion's Mane jellyfish is the killer. It is found from temperate waters to the Arctic.

Purple Jellyfish - Pelagia noctiluca
Avoid these

The slightly stinging Purple Jellyfish has only few catch tentacles trailing from its bell and five feeding tentacles surrounding its mouth. It can grow 40 cm across. When first discovered, this one glowed at night, presumably because it was feeding on sea spark dinoflagellates

Mushroom Cap Jellyfish - Rhopilema verrilli

The Mushroom Cap Jellyfish has a deep swimming bell without tentacles on its margin. It is a creamy while color with darker markings on the sturdy central tentacle structures. It grows up to 20" in diameter and although it has long finger-like appendages hanging from its feeding apparatus. It is not hazardous to people.

The Sea Nettle Chrysaora quiquecirrha, another stinging jellyfish.
This is the estuarine form; the open sea form is larger and more colorful.
The Sea Nettle has many more tentacles than the similar Purple Jellyfish.

Thimble Jellyfish Linuche unguiculata ( photographed in Cozumel Mexico )

A little off-topic here, but these tiny tropical jellyfish and their pinhead-sized larvae, also known as "Sea Lice", are responsible for "Seabather's Eruption" - an uncomfortable itchy rash that sometimes has more serious complications. In northern waters, a similar illness is occasionally caused by the larvae of certain sea anemones. I had no idea at the time, and they didn't sting me at all.



Although superficially similar to jellyfishes, hydromedusae are more closely related to sessile hydroids. They are much firmer and sturdier in body than jellyfishes. Most are small ( less than 1 inch in diameter ) and do not sting. Others, such as the large and very dangerous Sea Wasp ( 9", right ) do.

White Cross Hydromedusa - Staurophora mertensi ( see below )

The White Cross Hydromedusa is found along the coast from the Arctic to Rhode Island. At night it rises to just below the surface. It feeds on other medusae and crustaceans. In the northern part of its range, it is seen from spring through late summer. In the southern range, it is normally found from spring to early summer. It can reach 12" wide and 2" high, and is not dangerous to humans.

Many-ribbed Hydromedusa of the Aequorea species

The "many-ribbed" genus of hydromedusae are similar in appearance to clear jellyfishes, but lack obvious tentacles and do not sting when touched. These are among the largest hydromedusae known, up to 12" across, and the identity of their corresponding polyp stage is still a mystery. Hydromedusae are mostly water, and when they dry up they lose half of their diameter and almost all of their thickness, becoming sand dollar-sized thin, brittle discs.

Beached hydromedusae. By the time they get here, the surf has stripped
away all the tentacles, leaving just a harmless dying blob of goo.



Siphonophores are free-floating or swimming colonial hydroids. All siphonophores are predatory, and should be treated with respect for their venomous sting. Some of the individual animals along the length of the colony provide tentacles for defense (dactylozooids) and food capture, while others may function as swimming bells (nectophores), aid flotation (pneumatophore), provide additional defense (bracts), digest prey (gastrozooids), or serve for reproductive functions (gonozooids.) Whether siphonophores are single individuals or colonies of well-integrated polymorphic hydroid and medusoid individuals is a matter of debate among specialists.

The Portuguese Man-O-War Physalia physalia (above) is commonly observed in the open ocean and coastal seas, and is often mistaken for a true jellyfish. It is found throughout the world in warmer seas, and is most common in the summer months in shallow coastal waters. They are frequently found on exposed ocean beaches after strong onshore winds; they are rarely found in sheltered waters.

The Man-O-War gets its name from the float, which is a gas-filled bladder that can be up to 12 inches in length and rise out of the water as much as 6 inches. The float has a crest that is used much as a sail to propel the colony across the water surface when the wind blows. Clusters of colonial polyps are attached to the underside of the bladder for digestion and reproduction, with very long tentacles ( sometimes up to 32 feet ) extending from the suspended polyps. Man-O-Wars are hermaphrodites; the fertilized egg develops into a planktonic larval form that produces the large Physalia colony by asexual budding.

The Man-O-War's main food consists of surface plankton, although it can also take larger prey. Its tentacles have stinging cells called nematocysts that are capable of killing a fish up to 4 inches long. The poison secreted from the nematocysts of the Portuguese Man-O-War causes respiratory problems and muscle weakness. In humans, the sting of the Man-O-War can vary from extremely painful to incapacitating to fatal, depending on the severity and the victim's reaction.

Chain Siphonophore - Stephanomia cara ( see below ) - a swimmer rather than a drifter.

It is not hard to imagine how the hollow swimming polyps of the Chain Siphonophore could become filled with air or secreted gases and over time evolve into the float of the Man-O-War.

Comb Jellies


You cannot go diving in New Jersey waters without seeing Comb Jellies. Up close, rainbow-like rows of tiny beating hairs called cilia may be seen - the Comb Jelly's only means of propulsion. Comb jellies do not sting, but they are still voracious predators, feeding on anything they can engulf. At night they may phosphoresce - watch the boat wake as agitated Comb Jellies flash in the dark like depth charges. Cnidarians are exclusively marine, although some are tolerant of brackish water as well.

Leidy's Comb Jelly - Mnemiopsis leidyi

About two inches wide, Leidy's Comb Jellies range from Cape Cod to the Carolinas and are common in the Chesapeake Bay as far north as Baltimore. They have eight moving comb plates that move food toward the mouth. Marine labs use them to study bioluminescence and regeneration. Comb jellies are not true jellyfish - they have no stinging cells, although they are predatory, and have even been known to take small fishes !

Ovate Comb Jelly - Beroe ovata ( see below )

Comb Jellies are classed in a phylum of their own - Ctenophora. ( Pronounced 'tee-no-for-a', the C is silent. ) It has about 100 species in 5 orders. Comb Jellies live in all oceans, not caring whether it is hot or cold. Reproduction is sexual. The young resemble their parents and they can breed as soon as they hatch at just 1mm in length !

Sea Gooseberry - Pleurobrachia pileus

The Sea Gooseberry is another ctenophore like the Comb Jelly. Although they have tentacles, these creatures do not have stinging cells; instead, the tentacles use a sticky coating to trap plankton.

Sea Butterflies & Swimming Snails


Naked Sea Butterflies Clione limacina resemble angels. They have a spindle-shaped body up to 1 inch long that is bluish and transparent, with pink to red-yellow areas. The shell is absent. The head is well developed and clearly evident because of an indentation on the upper part of the body. The body has robust flaps ( mantle lobes ) that are used for propulsion. Although it looks like a jellyfish, the Naked Sea Butterfly is a gastropod mollusk, related to snails and sea slugs, and does not sting.

Naked Sea Butterfly Clione limacina

Atlantic Corolla - Carolla calceola ( see below )

The Atlantic Corolla is a swimming snail with a soft, transparent gelatinous body. It looks like a jellyfish but it is not. A truly planktonic opisthobranch that, being negatively buoyant, must swim with its large wing-like foot.

Horned Salp


Thalia democratica

Although they may superficially resemble swimming siphonophores, salps are actually free-living tunicates ( see Sea Squirts. ) there are 6 genera of salps and all are transparent.

Tunicates are much more advanced in the evolutionary scheme of things than jellyfishes, having, for example, a circulatory system. The larvae actually even have several features in common with vertebrates, including the precursor of a spinal cord, but these are lost in the sac-like adults. Salps do not sting.

A chain of 32 Horned Salps. Individuals are 1/4 - 1/2 inch in length.

These animals pump water through their body for respiration, feeding, and locomotion. They feed near the surface. Salps secrete a mucous film that runs along the body wall to the mouth, collecting particles from the surrounding water to feed on. Individual animals range in size from under an inch up to 8 inches, depending on the species. Salps often form long chains ( up to 90' ) of connected individuals. A common predator of salps that is often seen in local waters is the Sunfish, Mola mola.

Drifting In A Jellyfish Sea

Cover: Purple Jellyfish - Pelagia noctiluca

Text and images by Herb Segars

It's late summer and I am 20 feet below the surface of the Atlantic Ocean off New Jersey. I am wearing long underwear, a waterproof ( and leak-proof, I hope ) rubber suit, 40 pounds of dive gear and a 30-pound weight belt to keep me from bobbing to the surface. A slight current forces me to grip the anchor line with one hand and take photographs with the other. I see a possible subject 6 feet away and watch as it drifts closer.

In the blink of an eye, I have set my focus and triggered the camera. The two underwater flashes attached to the camera fire and I hope that the results look as good as I envision. Between frames, I monitor my air supply and my time underwater. Thousands of planktonic subjects float by in the hour that I am below. Today turns out to he a good day - I run out of film before my time or air expires. Back on the boat, I dry off, change film and wait the required 1+ hours before making my next underwater photographic journey.

A Many-ribbed Hydromedusa of the Aequorea species, with a hitchhiker.

Ovate Comb Jelly - Beroe ovata

Lion's Mane Jellyfish Cyanea capillata
being eaten by a Cunner Tautogolabris adspesus

White Cross Hydromedusa - Staurophora mertensi

Many-ribbed Hydromedusa of the Aequorea species

Leidy's Comb Jelly - Mnemiopsis leidyi

Chain Siphonophore - Stephanomia cara

Atlantic Corolla - Carolla calceola

Ovate Comb Jelly - Beroe ovata

Atlantic Corolla - Carolla calceola

Capturing the underwater realm on film is a long and painstaking process. All my underwater work off New Jersey happens in the spring, summer and fall. In a good year, I am able to make 70 dives and shoot 70 rolls of film. When strong winds and rough seas bring a season of had weather, the number of dives and rolls of film taken drop to fewer than 20. In comparison, on a typical topside nature photography trip, I can shoot 70 rolls of film in a week.

This article first appeared in New Jersey Outdoors - Summer 1999

Purple Jellyfish - Pelagia noctiluca

Longfin Squid


Loligo pealei

Size: to 17"

Habitat: Generally deep waters, but moves inshore in the summer. I have seen small ones at depths of 50-70 ft and babies in the rivers.


The squid is a mollusk, related to snails and clams. These animals travel in schools, swimming backwards by jet propulsion. Small specimens are nearly transparent except for the eyes. Tropical squids can show considerable intelligence and curiosity, but northern versions are, well, just stupid. I have seen huge schools of small transparent squids offshore, just their eyes visible, like black marbles. In the rivers, I have seen small schools of purple squids, and tiny colorless babies drifting in the current. All are predatory.

Longfin Squid in the wild

Most people only ever get to see them like this ...

... or this.

Squids spawn en masse. Each finger in these egg clusters was produced by a
single female. Northern Squid live less than a year, and die after spawning.
Better not to be a squid ! ( Mohawk )

Unfortunately, there are no octopus in diveable depths in the Mid-Atlantic region ( except for rare stragglers ) although they do come into shallow water north and south of here.

Common Atlantic Octopus Octopus vulgaris


I make no claim as to the accuracy, validity, or appropriateness of any information found in this website. I will not be responsible for the consequences of any action that is based upon information found here. Scuba diving is an adventure sport, and as always, you alone are responsible for your own safety and well being.

Copyright © 1996-2016 Rich Galiano
unless otherwise noted


since May 05, 2015