Daily News Photos by NICK SCHNEEMAN A few lonely boats were left to brave the waves breaking in Hull Bay, St. Thomas, on Thursday afternoon.

ST. THOMAS - Severe sea conditions battering the northern shores of the territory injured three swimmers at St. John's Cinnamon Bay on Thursday.

Injuries suffered by the visitors were a probable dislocated shoulder, a forehead abrasion and a fractured ankle, V.I. National Park Chief Ranger Mark Marshall said.

He also said that a fourth visitor reported an injured shoulder blade late Wednesday afternoon after being knocked around in the high surf.

The large swells pushing through the territory are being generated by an intense storm system east of Nova Scotia.

The National Weather Service has extended its coastal flood and high surf warning for St. Thomas and St. John until noon today.

A coastal flood warning means that flooding is expected and a high surf warning means that breaking waves are reaching 20 feet or higher and dangerous rip currents are present.

Rip currents are fast-moving belts of water channeling water out to sea, and they are the leading hazard to beachgoers - drowning about 100 people a year in the United States, according to the National Weather Service.

The entire territory remains under a small craft advisory, and St. Croix is under a coastal flood watch and a high surf advisory until noon today, he said.

A coastal flooding watch means flooding is possible and a high surf advisory means that waves less than 20 feet will hit the area in addition to beach erosion and rip currents.

The size and force of the swells peaked early Thursday morning and they are expected to taper off over the next several days, National Weather Service Meteorologist Brian Seeley said.

"An event this size, you just don't flip a switch and its gone," he said.

This is the first high surf warning ever issued by the National Weather Service's San Juan office.

The swells are hitting just as spring break and Holy Week visitors have poured onto the Virgin Islands and its beaches. Many Puerto Rico boats will attempt the trip to the Virgin Islands for a long holiday and V.I. government employees are on holiday through Monday.

Magens Bay on St. Thomas was packed Thursday and no injuries were reported, Hubert Brumant, the authority's general manager said.

He said lifeguards kept children away from the water as a safety precaution.

The authority did bar swimming at Lindqvist Beach on Thursday because of the rough sea conditions, he said.

V.I. Territorial Emergency Management Agency officials were out early Thursday morning assessing sea and beach conditions territorywide.

VITEMA Acting State Director Steve Parris said any impact on St. Thomas and St. John due to sea conditions was minimal.

Ferries and barges operated as usual Thursday, however, one barge tied up for the night Wednesday in Cruz Bay instead of Red Hook because of the rough seas, he said.

Parris advised residents and visitors to be cognizant of the potential dangers of the current sea conditions, especially rip currents.

"We are entering a long weekend for the Virgin Islands and we want everyone to remain safe," he said.

VITEMA's deputy director on St. Croix, Jacqueline Heyliger, said she surveyed the northern side of St. Croix early Thursday and found no major impact or flooding.

"We fared pretty well," she said.

Puerto Rico is seeing some flooding, according to the National Weather Service.

The Associated Press reported that authorities in Puerto Rico closed the San Juan harbor Wednesday and canceled ferry service to the tiny islands of Vieques and Culebra. In the Dominican Republic, popular beaches along the northern coast were closed through today. Puerto Rico also sent cargo ships from its port ahead of schedule to beat the storm and about 300 families in the northern coastal town of Loiza, east of San Juan, were temporarily relocated as a precaution.

U.S. Coast Guard Lt. Cmdr. Jose Quinones said the San Juan port remained closed on Thursday and no boating accidents have been reported.

"It's still rough out there and we are continually assessing the situation," he said.

A major destination for boaters coming from Puerto Rico is Yacht Haven Grande marina on St. Thomas.

Yacht Haven is "110 percent full" this weekend, despite the rough seas, marina manager Kristen Fritz said.

All the slips are occupied, along with the fuel dock, she said, and a couple of boats that had been planning to leave by the weekend decided to stay because of the weather.

Of the yachts docked, 25 are from Puerto Rico, Fritz said. Only four Puerto Rico boats canceled their visit.

The groups who came over reported that the trip was not too bad, Fritz said.

"There are more big rollers as opposed to the high chops," she said. "As far as coming over here, it wasn't too horrible."

- Daily News reporter Lynn Freehill contributed to this report. Contact Tim Fields at 774-8772 ext. 364 or e-mail tfields@dailynews.vi.