JUPITER, Fla. » The Coast Guard searched "aggressively" off the Florida coast and friends combed the shoreline Monday for any sign of two teenage fishermen, described as experienced boaters, who went missing three days earlier after setting out for the Bahamas on a stormy afternoon.

What began as a teenage summer adventure — a chaperone-free getaway on the high seas — took an ominous turn after the 19-foot boat that carried Perry Cohen and Austin Stephanos was found capsized and days of searches proved fruitless. But authorities and the boys’ families held out hope, saying the teens were consummate seamen and a rescue is still possible.

"Our intentions are to continue to search aggressively," Coast Guard Capt. Mark Fedor said at a news conference Monday evening, but that the decision was being reevaluated daily. Earlier in the day, Coast Guard Petty Officer Steve Lehmann said the search was going on under "the highest level of optimism." He declined to say how long it would continue beyond "the time being."

Crews studied ocean currents and zeroed in on an area off Jacksonville as the most likely position for the boys Monday. Meanwhile, the teens’ families and a famous neighbor — NFL Hall of Famer Joe Namath — pledged to walk the beaches beginning in their hometown of Tequesta in hopes of finding clues.

"We need every clue and we need everyone’s help," said Nick Korniloff, the stepfather of Perry.

The boys were last seen Friday afternoon buying $110 worth of fuel near Jupiter. Officials said they departed around 1:30 p.m. Weather reports for Friday say storms reached the Jupiter-Tequesta area around 4 p.m., and thunderstorms with heavy rains were expected there until sunset. Fedor called it "typical South Florida weather" and said there still was no clue why the boat capsized.

One life jacket was found near the boat, and it was unclear how many life jackets had been on board. Water temperatures were warm and not cited as a factor in the boys’ survival.

The teens’ vessel was found Sunday off Ponce Inlet, more than 180 miles north of where the boys began their journey. Though the boat was overturned it did not appear damaged. No foul play was suspected.

The Coast Guard said Monday that by midnight, its search will have covered an area the size of West Virginia. Searchers were using helicopter, boat and airplane, and local authorities and the USS Carney also joined the efforts to locate the boys. The families of the teens are offering $100,000 reward in the search.

The teens were believed to have been heading toward the Bahamas, about 75 miles southeast of Tequesta.

"It’s a lot of water out there," Namath said. "We just keep on looking till we get an answer."

Austin’s mother, Carly Black, told WPBF she never would "bat an eye" at the boys’ ability on the seas.

"This isn’t something that he’s new at," she said. "I think they feel better on the boat than they do on land."

Florida requires minors to have boating safety instruction in order to operate a boat of 10 horsepower or greater, but no licenses are issued. It was not immediately clear whether the boys had undergone a safety class.

Korniloff said he was focused on finding the boys and wouldn’t comment on questions about whether 14-year-olds should be allowed to venture so far alone. He said the boys had been "raised on the water" and were taught how to navigate safely.

"If you put two pretty girls in front of them and two fishing rods, they’d grab the fishing rods first," the stepfather said.

Still, Lehmann said boaters of any age and experience level could encounter danger.

"Regardless of how experienced you are in the water, things can happen," he said. "Things befall even the most surefooted of mariners."