HOUSTON -- The Coast Guard used boats, a helicopter and airplanes Saturday to search for four fishermen who went missing off the Gulf Coast after their boat sank. A crew member was rescued from a life raft Friday.The Coast Guard received a distress signal from the 50-foot boat at 3:30 a.m. Friday, Petty Officer Richard Brahm said. It began sinking about 115 miles southeast of Galveston, not far from the Louisiana state line.Weather was bad at the time, Brahm said. Sustained winds were strong, at 33 mph with gusts of up to 40 mph, he said. The water was 50 degrees, and sea swells were 10 to 15 feet, which was enormous for the 50-foot boat the men were in, he added.About five hours after the distress signal, at 8:30 a.m. Friday, a search team found crew member John Robinson on a life raft. Robinson was returned to Galveston and told the Coast Guard he was unsure what had happened to the other four men on board, Brahm said.Overnight, the Coast Guard used one cutter and one aircraft to search an area slightly smaller than the state of Delaware. It added two more aircraft to the hunt at daybreak Saturday, Brahm said."We're going to keep searching until someone tells us to stop," he said, noting that the Coast Guard uses a variety of factors to determine whether the men could still be alive.Brahm said the Coast Guard would continue searching through Saturday night.