Shark sightings, stinging jellyfish and running out of sunscreen may top the list of the biggest worries for Long Island beachgoers looking to cool off this summer.

But as Hurricane Erin pulled away — and with two recent drowning deaths in the metropolitan region — water safety experts are advising about a less obvious, but undoubtedly greater risk: dangerous rip currents.

On Aug. 11, Liudmila Marchenko, 77, of Brooklyn, was pulled unresponsive from the rip currents of Manhattan Beach by lifeguards, authorities said. Marchenko was taken to NYC Health + Hospitals/South Brooklyn Health where she was pronounced dead.

Earlier that day, on the Jersey Shore, a swimmer died after he and six others got trapped in a rip current off an unguarded beach in Seaside Heights, officials said.

Deadly currents

Rip currents are powerful, narrow channels of fast-moving water — often moving at speeds of 8 feet per second or faster than an Olympic swimmer — that are most prevalent along the East, Gulf and West Coasts of the United States, according to the National Oceanic and Atmospheric Administration.

Typically, rip currents can form, disappear and re-form quickly along the shoreline, according to NY Sea Grant at Stony Brook University, a science-based organization.

While rip currents, which form at breaks in sandbars, or near jetties and piers, don't pull swimmers under water, they can carry them a far distance from shore. 

And they can prove deadly even for seasoned swimmers.

Rip currents are responsible for more than 100 deaths each year and 80% of all lifeguard rescues, according to the United States Lifesaving Association.

 The rip current risk has been high on Long Island as Hurricane Erin passed by in the Atlantic.

"Even though it could be hundreds of miles away, we sometimes see the effects on the beaches days in advance of it coming close to Long Island," George Gorman, state parks regional director for Long Island, said of major storms. " ... You have to be careful of the Atlantic Ocean. In one area, you could have a light to moderate rip current. But in another area you could see a severe rip current."

'Don't panic'

There were 84 drowning deaths statewide in New York last year. That included 24 in Suffolk County, up from 15 one year earlier, according to local statistics.

But more than 80% of drowning deaths, experts said, occur in backyard pools as opposed to the open waters of the Atlantic.

Rip currents, however, present different challenges.

The most important tip, experts said, is not to fight the current, as even the best swimmers will tire out and potentially drown.

Instead, experts suggest turning sideways, parallel to the shore, and to wade, swim or tread water until out of the rip current before moving back toward shore at an angle away from the rush of water.

In addition, officials advise the public to never swim alone and always near a lifeguard.

"First of all, don't panic," Alissa Magrum, executive director of the California-based National Drowning Prevention Alliance, said of getting trapped in a rip current. "If you're able to wave or yell for help, do that. And if you're able to, flip over and float on your back. Do not fight the current. A lot of times, people try to swim back through the current, and then they get worn out. And that's when we see drownings."

Most Long Island beaches post flags by lifeguard stations, alerting swimmers to rip current conditions. For example, a green flag indicates the water is safe; yellow indicates some rip current activity is expected; and red means conditions are hazardous and the water is closed to swimming.

Wyatt Werneth, spokesman for the Florida-based American Lifeguard Association, adds that beachgoers who see a swimmer in trouble because of rip currents should first alert a lifeguard.

But if a lifeguard is not around, he said, never enter the water without a flotation device, as it's not uncommon for people to die trying to rescue rip current victims.

"Look around for something that floats," Werneth said. "A Boogie Board. A noodle. A cooler. Even a beach ball."