An early morning fire Sunday on St. Helena Island sank not only a boat but the longtime dream of a Hilton Head Island firefighter, his coworkers said.

Dan Thomas was preparing for a retirement of living on the boat and sailing with his wife, said Battalion Chief Michael Mayers with the Hilton Head Island Fire and Rescue Division.

But at about 7 a.m. Sunday, his catamaran went up in flames off St. Helena Island, in the area of St. Helenaville, said Lee Levesque, Lady's Island-St. Helena Fire Department spokesman.

Thomas could not be reached for comment Monday.

By the time firefighters arrived, the boat was ablaze, tipped over on the dock and sinking, Levesque said. It went under within 30 minutes, he said.

The cause of the fire is unknown.

"Unfortunately, we don't have much," Levesque said. "The boat ended up at the bottom of the river."

The flames were initially reported as a brush fire by nearby residents, he said.

Firefighters had trouble reaching the burning boat because the only access was by a narrow causeway, Levesque said. They had to leave the firetruck on the road and use an all-terrain vehicle to reach the dock.

The American Red Cross is helping the couple by providing money for clothing destroyed the fire and comfort kits with personal hygiene items, according to a news release.

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Boat catches fire early Sunday in St. Helena, March 12, 2012