Jellyfish (also called Sea Nettles) are in the Chesapeake Bay, but not everywhere. The beautiful, but dangerous, creatures are found mainly in the middle and lower sections of the bay, where the water is saltiest.

When they show up varies from year to year.

What are Jellies/Sea Nettles?

Chesapeake Bay region residents use the terms “jellyfish,” “jellies” and “sea nettles” interchangeably. Which term is usually based on where they grew up. Technically, a sea nettle is a category of jellyfish.

Jellyfish are typically, but not always, clear and that makes them difficult to see. They have long tentacles dangling as they pulsate through the murky Bay water.

You know when you come across one. First, you’ll notice the tentacles; they feel like hair floating through the water. Then you feel the sting that doesn’t go away any time soon.

Once they arrive, they’re going to hang around until about October.

Types of Jellyfish in the Chesapeake Bay

In the Chesapeake Bay, you’ll most likely come across moon jellyfish — peaceful, pretty, blobby things floating around. Moon jellies sting, but it’s a small hurt if you even notice it

You might see Salps, but they’re mainly at Ocean City. Salps are small and don’t sting.

Moon jellyfish are also common in the Chesapeake Bay, but they’re harmless to most people. They have a wider bell and shorter tentacles. 

(Photo courtesy of the Chesapeake Bay Program)

Salp (tunicatesea squirt) are firm but gelatinous. They also have a “primitive eye” that can be seen in this picture. These were found in Ocean City. 

salp (tunicatesea squirt)

(Photo courtesy of the Assateague Island National Seashore)

There’s also a Bay Nettle unique to the Chesapeake Bay and a larger ocean-going Sea Nettle. The Bay Nettle is smaller with longer tentacles than the Sea Nettle.

The Bay Nettle helps oysters by eating certain preditors. The sting is “moderately painful, but not dangerous unless there is an allergic reaction,” according to the Virginia Institute of Marine Science.

Man of War nettles are big and pack a painful brush as they go by. They tend to stay closer to the ocean.

How to Avoid Jellyfish

The government tries to figure out where they are and provides some predictions.

NOAA, National Oceanic, and Atmospheric Administration, actually has a sea nettle prediction website, but it’s not always working. 

“The maps are experimental and depict the probability of encountering the sea nettles, Chrysaora chesapeakei in the Chesapeake Bay and its tributaries.”

National Oceanic and Atmospheric Administration

The Sea Nettles Probability of Encounters website has a Chesapeake Bay map. Click on the section of the bay where you are and it’ll give you a percentage chance that you’ll run into jellyfish. 

A more reliable source is found in the data being filed from the Chesapeake Bay buoys. This is a dense website, but you’ll find a useful Interpretive Buoy System chart. 

Click on the buoy location closest to you. Several lines of information pop up. There’s a line in the middle with the percentage of sea nettle probability where that buoy is located. 

The key to avoiding jellyfish is to find freshwater. The buoy chart also has water salinity and water temp. NOAA says, “sea nettles are found within a relatively narrow, well-defined range of temperature (79-86° F) and salinity (10-16 PSU).” 

Another way to check for jellyfish at the beach where you’re going is to call the park where the beach is located. However, that works for state parks and some county parks where someone is collecting fees. Many of the rural counties don’t have people answering phones on the weekends.

Where to Swim When Jellyfish Arrive

There are several Chesapeake Bay beaches that are just out of jellyfish range. The northern part of the Bay is pretty good year-round.

Privately-owned beaches in the briny Bay areas often surround the swimming area with nets protecting swimmers from stings.

Here are some mid to upper Chesapeake Bay beaches that are less briny or are surrounded by nets.

There’s also a Bay Nettle unique to the Chesapeake Bay and a larger ocean-going Sea Nettle. The Bay Nettle is smaller with longer tentacles than the Sea Nettle.

The Bay Nettle helps oysters by eating certain preditors. The sting is “moderately painful, but not dangerous unless there is an allergic reaction,” according to the Virginia Institute of Marine Science.

Man of War nettles are big and pack a painful brush as they go by. They tend to stay closer to the ocean.

What to Do When Stung by Jellyfish

One solution: You could keep baking soda or vinegar handy. Those, combined with seawater, are recommended for washing away the micro-sized tentacles. 

Another solution: cover the area with a cold compress. Then, using calamine location, mild hydrocortisone, or taking an antihistamine. 

If experiencing a severe reaction, seek medical care. 

The only way to avoid getting stung in jellyfish-infested waters, according to the Chesapeake Bay Program, is by wearing a wetsuit — or pantyhose.

Seriously. Pantyhose. But try finding that these days.

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