Enormous, stinking blobs of light-brown mucus harboring bacteria and viruses cover swimmers in slime and get caught in nets in the Mediterranean Sea, and the problem is getting worse because of warming sea waters, according to National Geographic.

The sheets of mucus-like material, which begin as clusters of mostly microscopic dead and living organic matter, have been forming more frequently, spreading into new areas and lasting into the winter.

Some of them can reach an astounding 124 miles long, forming gigantic gelatinous masses that are not just a nuisance, but a health hazard to humans and marine life as well.

Researchers at the marine science department at the Polytechnic University of Marche in Italy say the blobs harbor dangerous pathogens including potentially deadly E. coli.

These clusters of organic matter – known as marine snow – gather mass by picking up tiny sea creatures like small crustaceans.

They’re too dense to swim inside, but people who swim near them can develop skin conditions such as dermatitis. The masses can also trap and suffocate animals.

Serena Fonda Umani, co-author of the new study, says she dived into marine snow once, describing the texture of the slime that was all over her wetsuit and hair as "sugar solution".

"The suit was impossible to wash totally, because it was covered by a layer of greenish slime. It was a nightmare."