In what has become a rite of summer, it’s nearly Sargussum season on Florida beaches. In many recent years, thick brown mats of a macroalgae named Sargussum start washing up on the shorelines, sometimes reaching several inches in depth in early summer, and those mats linger until well into the season.

Sargassum often comes with a pungent stench attached to it — something between sewage and rotten eggs — due to the mats off-gassing Hydrogen Sulfide and Ammonia, among others. Hydrogen Sulfide smells like rotten eggs, and ammonia is most commonly linked to a stale urine smell. This makes a sargassum-covered beach a wholly unpleasant experience, and that’s before the brown water is created in the surf by Sargassum decaying in the water.