Palm Beach, Fla. ? Treacherous rip currents along the Florida coast in the past week have killed at least four beachgoers, led to dozens of rescues and forced lifeguards to issue an unpopular warning in the middle of spring break: Stay out of the water.

One current was so overpowering that an 83-year-old woman, Madeline Roberts, was dragged away north of Palm Beach after a wave knocked her down as she took a stroll along the water’s edge Sunday. Rescuers pulled her out along with an 82-year-old woman who had jumped in to save her. Roberts survived; the friend died hours later.

“It was very frightening for them. This is something they do often and they were just powerless,” said Sharon Martinelli, Roberts’ daughter. “My mom’s walked on the ocean all her life.”

This week’s deaths were all blamed on rip currents, which are rushing channels of water that can carry away even the best swimmers. Although the currents do not drag swimmers under water, many people panic, become tired and drown as they try to swim back to shore.

The four deaths in Florida in one weekend have made the past week a particularly deadly one, considering the currents on average kill about 19 people in the state during the entire year.

Rip currents also occur along the Pacific Coast and the Great Lakes. They pose more danger to swimmers than either sharks or hurricanes do and were responsible for 16,300 rescues in 2003, according to the U.S. Lifesaving Assn.

Rip currents, often incorrectly called riptides, pull water in one direction, seaward. They can be especially treacherous because the water’s surface remains smooth. Riptides involve opposing currents and can churn the water violently.

Swimmers caught in a rip current are urged to try to swim parallel to shore to get out of it.

March typically is the worst time for rip currents in Florida because it brings more wind — and more tourists — than any other month.

Lifeguard Sean Maxwell keeps an eye on the surf for swimmers in Fort Lauderdale, Fla. Tourists and spring breakers who planned to soak up some sun and cool off in the ocean this week are being warned: Don't go in deeper than your ankles, and if you can't swim, don't go in at all. Those warnings from lifeguards along the East and Gulf coast beaches were prompted by treacherous winds and surf, dozens of rescues and four deaths in rip currents.

Last year, after at least 23 people drowned on Florida Panhandle beaches, new efforts were made to warn of rip currents, including roving patrols that were credited with one rescue this month.

Tourists and spring breakers who planned to soak up some rays and cool off in the ocean this week also are being warned: Do not go in deeper than your ankles, and if you can’t swim, don’t go in at all.

“A lot of people come to the beach and it’s such a carefree environment, it’s easy to forget the dangers,” said Mark Hassell, lifeguard supervisor for the town of Palm Beach.

Along the beaches of Fort Lauderdale, stiff 15-to-25 mph winds snapped yellow caution flags near lifeguard stations. Most beachgoers relaxed in deck chairs instead of tumbling in the crashing waves.

“I wouldn’t take any chances going in,” said John Moran, a retiree from White Oak, Pa., who was stretched out on beach chairs with his wife.

Despite the warnings, Greg Dulkowski took a dip in the 72-degree waters.

“It was refreshing, but I went out about thigh deep and it about knocked me over,” Dulkowski said. He kept a tight hold on his 5-year-old great niece’s hand when she wanted to get her feet wet.

“That’s as far as she’s going in today,” he said.