Take care if you're heading down to the Florida beaches this summer, there's something unpleasant lurking in their waters. No, not Jaws. Or crocodiles. 

The Florida Department of Health has recently warned beachgoers about an “eruption” of stinging microscopic "sea lice”. The worst-affected beaches are in Pensacola, although it is possible the infestation could hit many beaches along 400 kilometers (250 miles) of Florida's southern coastal area. The Department of Health said lifeguards will stick up purple flags in order to alert swimmers about the presence of sea lice.

Sea lice is just a slang name given to these irritating critters. In South Florida’s case, they are actually the larval form of the thimble jellyfish (Linuche unqui culata). Although barely even visible to the naked away, the larvae are able to shoot out nematocysts, the specialized cell in the tentacles of a jellyfish that contains a barbed venomous hook.

Contact with the of nematocysts of these tiny organisms will bring out a desperately itchy rash. As you can see from images of an affected person, it can get pretty nasty. It’s not unusual to see over 100 stings on a single person’s body. Usually, the itchiness and discomfort will resolve within a week or so, however, some people can experience nausea, vomiting, diarrhea, headache, difficulty sleeping, and muscle spasms. Not fun.

"They aren't very intense, which is why we call them sea lice and not sea hornets or sea wasps," Dave Greenwood, Pensacola Beach’s director of public safety, told the Pensacola News Journal.

“It’s just one of those you have to deal with when you go into the Gulf of Mexico. You are a land animal and the Gulf is not our native environment.”

If you’re planning a trip to the beach in South Florida, the Department of Health has advised swimmers to not wear T-shirts in the sea, as the sea lice can easily get trapped under clothing and actually end up stinging you more. For that very reason, they are also recommending people wear as skimpy as possible swimsuits. Once you’re out of the water, change out of your swimsuit ASAP and shower with fresh water.

The sea lice have hit Florida in previous years, with records of outbreaks dating back to as early as 100 years ago. Nevertheless, the eruptions of sea lice appear to have intensified in the last four years.

There was an Australian outbreak of “sea lice” in August 2017. In this case, it was a totally different species and they were A LOT more aggressive because, you know, Australia.