An 18-year-old male drowned in the waters off Ocean City after being caught in a rip current. (WJZ Video)

The Coast Guard rescued three people near Ocean City's inlet Wednesday when their 17-foot boat capsized, and a Virginia teen drowned in a rip current there Tuesday as town officials limited beachgoers to wading as Hurricane Cristobal continues to churn up Mid-Atlantic waters.

This summer has been the deadliest in years for swimmers at Maryland's oceanfront resort, with the first reported drownings while lifeguards were on duty since 2007, according to the Ocean City Beach Patrol.

Meteorologists and lifeguards expect the seas to calm somewhat in time for the busy Labor Day weekend, as Cristobal speeds north into colder waters and away from the Delmarva Peninsula. But if this summer is any indication, dangers could remain for swimmers even after the storm passes — and with many schools in session there will be fewer lifeguards to protect them.

Swimming restrictions remained in place Thursday afternoon, according to the beach patrol, though swimmers could be seen going further than the temporary knee-deep rule allowed. Wave heights were reported at 4 feet, with a dangerous shore break, according to the National Weather Service.

Cristobal's effects could be felt into Friday, and Ocean City police spokeswoman Lindsay O'Neal said the swimming restriction might be extended into Labor Day weekend, depending on conditions. The National Weather Service warned of dangerous surf conditions through at least 8 p.m. Thursday, with waves expected to reach heights of 5 feet to 6 feet Thursday morning before gradually receding.

"Once the ocean gets stirred up, it doesn't just go all of the sudden from high waves to normal," said Brian Wimer, a senior meteorologist with AccuWeather.com. "It's a gradual process of getting lower waves."

The storm was about 300 miles southeast of Cape Hatteras, N.C., as of Wednesday evening, with maximum sustained winds of 75 mph, making it a weak Category 1 hurricane. Some strengthening was possible into Thursday, but after that, Cristobal is expected to move into colder water and lose its tropical cyclone characteristics.

Still, the storm was kicking up big enough waves to capsize vessels even larger than the 17-footer that overturned near Ocean City's inlet Wednesday afternoon. After receiving a report of an overturned vessel about 4:30 p.m., the Coast Guard said it diverted a 47-foot lifeboat already out for training to rescue all three people who were aboard the capsized vessel.

The beach patrol attributes this summer's dangers to unusually rough surf that develops in some years but not others, causing waves to break violently onto shore and creating widespread and frequent rip currents. Some questioned whether offseason beach replenishment played a role, a concern town officials played down.

"There's always rips out there regardless, but this summer it just seems way more than normal," said Matt Landon, a manager and surfing coach at K-Coast surf shop. "This is the first summer I remember there being three drownings."

Jose Maudiel Hernandez, an 18-year-old from Manassas, Va., was swimming near the inlet at the town's southern end shortly after 6 p.m. Tuesday when he appeared to be caught in a rip current and struggled to get back to shore, witnesses told first responders. Lifeguards had gone off duty about 40 minutes earlier.

Witnesses saw a wave overtake Hernandez, and he did not resurface until rescuers pulled him out 13 minutes after the initial distress call. He was treated at the scene then taken to Atlantic General Hospital in Berlin, where he was pronounced dead.

Two 17-year-old boys drowned in Ocean City within a span of two weeks in June.

Multiple drownings have not occurred in Ocean City since 2006, when a Columbia man and his 15-year-old daughter died when he tried to rescue her from a rip current. A 19-year-old Morgan State University student drowned in a rip current in 2007 while lifeguards were on duty.

Nearly all of the rescues lifeguards perform each year are related to rip currents, said Butch Arbin, captain of the beach patrol. The swift-moving channels of water flow from the beach out toward the ocean, pulling sand, seaweed and sometimes swimmers along with them.

Rip currents appear as channels of churning, choppy and often murky water that break up waves and run out from the shore. Swimmers are advised not to fight rip currents but to swim parallel to shore to escape them and avoid being pulled farther out to sea.

Typically, rip currents form when water that waves pushed close to shore gets trapped between the beach and a sandbar just offshore. The water pressure stresses the sandbar, eventually breaching it and causing the water to flow rapidly back out to sea.

Arbin said there is no unusual explanation for this summer's increase in rip currents, which can depend on tides, winds, ocean depth and other factors.

"A lot of things go into it, and the biggest factor is last year, we just did not get the big surf," something that is uncommon for July and August, Arbin said. "This summer is a more typical summer compared to last summer."

But surfers who know the waves well said they wonder if changes in the beach profile from offseason beach replenishment is a factor.