Published: Jul 30, 2014 5:05 PM EDT

FORT MYERS BEACH, Fla.- Fear of red tide is spreading among beachgoers in Southwest Florida. A massive patch of the algae bloom is located off the Gulf coast, just north of Saint Petersburg, and it's slowly drifting southward.

Though it was a beautiful afternoon on Fort Myers Beach, far out there lurks a naturally occuring phenomenon that can make people sick, and kill fish and manatees.

Visitors and people who work in the hospitality industry are concerned. Algae causes red tide, and the bloom in the Gulf measures 80 miles long and 50 miles wide. That makes it 4,000 square miles, which is more than three times the size of Rhode Island.

"Spatially, this is the largest bloom since 2006," said Brandon Basino with the Florida Wildlife Commission in St. Petersburg.

Red tide releases chemicals into the air, and makes it hard for people to breathe.

"You start coughing and you feel a scratch in throat...You are not sick, but you have this hack, ya know," said Paul Adamick.

"It will kill commerce. People will not want to spend their vacation and money on a place they can't enjoy," said Judy Bishop.

Places like the Silver Sands Villas could be affected. The business is enjoying the best summer in years, and workers are worried.

"If it gets worse, it'll slow down the locals coming here, and if news gets out, visitors will delay their vacations also," said Kim Clark.

Everything depends on whether the bloom continues to drift south, and move closer to shore. Right now, nobody can predict for sure where it might go and when.