Question regarding the lagoon at Barra de Potosí

Ceratopogonidae, commonly known as biting midges or no-see-ums, are a family of small flies in the order Diptera. They are known for their tiny size (1-4 mm) and the fact that only the females bite, requiring blood for egg production. These insects are found in various aquatic and semi-aquatic habitats worldwide, and their bites can cause itchy welts or blisters. Or if it's in the water Swimmer's itch is an allergic reaction to tiny parasites that burrow into your skin while you're swimming or wading outdoors.

Greetings, Friends. On a recent outing to Barra de Potosí, I decided to swim in the lagoon. The only other time I had done that, the lagoon was open to the ocean. This time, the lagoon was closed to the ocean. There were other folks swimming in the lagoon so my assumption was that it was safe. After spending some time in the water, I felt as if I something was biting me. The bites weren't painful enough to warrant jumping out of the water immediately. Big mistake. Within a day, I was covered with a few dozen bite marks similar to mosquito bites. They itch tremendously. Has anyone ever experienced this or does anyone have any information about what these critters were?

Sounds like the jejenes got you. No-see-ums. Those phuqrs tear me up! It's been extremely odd that we haven't seen any on Playa Principal this year.

OK, I have another thought. We have swam in a number of rivers in Mexico, the first time we had issues with bites was in the Usumacinta, between Chiapas and Guatemala. Everyone was swimming, and they laughed at us when we reacted to the small, guppy sized fish biting us! Not really bad, but an eyeopener We have run into them in other rivers and river mouths too.

Many thanks to everyone. Thankfully, whatever the little monsters were, the bites are slowly disappearing and the itching is almost gone. Not sure if I am ever going to swim that lagoon again! The ocean is just fine.

My daugter got the rash as well when we stayed out in Playa Blanca and visited beautiful Barra. She say in the lagoon water. From the internet.....
Is this sea lice or jellyfish? Serious or not?
A rash from jellyfish larvae, also known as seabather's eruption or "sea lice," appears as a red, itchy, bumpy rash, sometimes with blisters, that occurs mostly in areas covered by a bathing suit or hair. It's caused by tiny jellyfish or sea anemone larvae getting trapped against the skin and releasing stinging cells, resulting in an irritating, inflammatory reaction. You can find pictures of this rash, which resembles a severe case of flea or mosquito bites, by searching for "seabather's eruption rash" or "sea lice rash" online.

What it looks like
Red, itchy bumps or blisters: that are raised and can be hard or soft.
Small, clustered red spots, similar to flea bites.
Appearance in specific areas, typically where clothing or hair traps the larvae, such as the groin, back, chest, or under a bathing suit.
Where to find images
Search for "seabather's eruption rash" to find medical illustrations and patient photos showing the rash.
Use terms like "sea lice rash pictures" to see examples.
MedicalNewsToday and CNN offer visual examples alongside descriptions of the rash.

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☀️ Princess