Few are surprised when they encounter a bit of seaweed floating in the ocean, or washed up on the beach. But the overabundance of sargassum has caused issues in recent years.

National Geographic explains, “since 2011, vast quantities have washed up on Caribbean coastlines, from the Lesser Antilles to Mexico’s Yucatán peninsula.”

Now, experts note, the giant blob of seaweed is washing up on Florida’s beaches.

If you’re planning to be Florida, Mexico or the Caribbean, here’s what to know about the sargassum problem.

What Is Sargassum?

The National Oceanic and Atmospheric Administration defines sargassum as, “large brown seaweed that floats in island-like masses and never attaches to the seafloor.”

The sargassum blooms in the Sargasso sea. But its presence in the Atlantic Ocean is so vast that NASA can detect it. Experts say the blob is about 5,000 miles wide.

Not only is sargassum unsightly, it has a terrible odor that is off putting to beach-goers and animals. But the potential health effects are of even greater concern, especially for those with respiratory issues.

Kait Parker, an atmospheric scientist at the Weather Company, said to Newsweek, “anyone with compromised lung function should avoid areas with sargassum blooms—when the seaweed decomposes, it releases hydrogen sulfide [the smell of rotten eggs] and can be a respiratory irritant.”

Parker also urged people not to consume sargassum, due to the presence of arsenic and cadmium.

Removing The Sargassum Is An Arduous Task

There’s so much sargassum on the beaches that a simple shovel isn’t enough.

In Guadeloupe, an excavator had to be brought in to remove it. The Grenville Bay coastline in Grenada was also overrun with the dead seaweed.

High end resorts in Mexico do what they can to clear their beaches. However, Journey Mexico reports, “the majority of low-budget hotels and hostels do not have the means to clean their beaches on a daily basis.”

Meanwhile, UHD Walk posted a video showing masses of dead sargassum on the shores of Miami Beach.

The culprit? Well, there are two. The first is human activity, namely “fertilizer runoff and sewage dumped into the ocean.”

That, and rising ocean temperatures, provide an ideal environment for sargassum to thrive.