ST. PETERSBURG, Fla. (AP) — Stinging jellyfish, rays with their whip-like tails and sharks on the hunt are some ocean hazards that might typically worry beachgoers. But rip currents are the greatest danger and account for the most beach rescues every year.

Six people drowned in rip currents over a recent two-day period in Florida, including a couple vacationing on Hutchinson Island from Pennsylvania with their six children and three young men on a Panhandle holiday from Alabama, officials say.

About 100 people drown from rip currents along U.S. beaches each year, according to the United States Lifesaving Association. And more than 80% of beach rescues annually involve rip currents.

The National Weather Service lists 16 known deaths so far in 2024 from rip currents in U.S. waters, including the Florida fatalities as well as eight deaths in Puerto Rico and two in Texas.

Here are some things to know about rip currents:

What is a rip current?

Rip currents are narrow columns of water flowing rapidly away from the beach, like a swift stream within the ocean. They don’t pull swimmers under water, but can carry them out a fair distance from shore.

Low spots along the beach, or areas near jetties or piers, are often where rip currents form. They can be connected to stormy weather but also sometimes occur during sunny days. They can be hard to detect because the surface water often appears calm.

The current can flow as swiftly as eight feet per second (3.2 meters per second), faster than even a strong swimmer can overcome, according to the National Oceanic and Atmospheric Administration.

“If you’re caught in one and you try to swim straight in, you’re not going to be able to,” said Daniel Barnickel of Palm Beach County Ocean Rescue.

How can someone escape a rip current?

The most frequent advice from beach rescue teams and weather forecasters is to not panic and look for a chance to swim parallel to the shore until the swimmer is out of the rip current’s grip. It will eventually dissipate but might leave the swimmer out in deeper water.

It’s nearly impossible to fight the current directly. Many swimmers who get in trouble tire themselves out trying to get back to the beach, lifeguards say. If possible, it’s best to swim near a lifeguard station.

“Most of our rip current rescues happen outside the guarded areas because we’re not there to prevent it from happening,” Barnickel said.

What warning systems exist for rip currents?

Flags with different colors are used to warn beachgoers of various hazards.

Three flags warn of surf and rip current conditions. Red means a high hazard, yellow means a moderate threat and green means low danger. There’s also purple for dangerous sea life, like jellyfish, and double red when a beach is closed for any reason.

The National Weather Service posts rip current risks on its websites around the coasts and has developed a computer model that can predict when conditions are favorable for their formation up to six days in advance for the U.S. East and Gulf coasts, Puerto Rico, Hawaii and Guam.

“Before this, forecasters were manually predicting rip currents on a large section of the ocean twice a day and only a day or two into the future. The earlier prediction has potential to substantially increase awareness and reduce drownings,” said Gregory Dusek, a NOAA scientist who developed the model, in a post on the agency’s website.

High risk warnings were posted for most Florida beaches last week, when the drownings occurred.

Should someone attempt a rip current rescue?

It can be dangerous to try to rescue someone caught in a rip current, officials say. Often the people trying to perform the rescue can get into trouble themselves.

It’s best to find a lifeguard, if there is one, or call 911 if a struggling swimmer is spotted. People on shore can also try to tell the person to swim parallel to shore.

“Never swim alone. And always make sure that there’s an adult. And make sure that you don’t overestimate your abilities. Know your limits,” Barnickel said.