CORONADO — Rich Cleveland first tried to get through Hell Week to become a Navy SEAL in January. He got hypothermia and passed out. The second time, in March, he broke his leg.

Cleveland's third try, two weeks ago, didn't begin badly. For 24 hours, he and the rest of Class 172 tossed 250-pound logs and then kicked them up sand berms, rowed and then shoulder-pressed inflated rubber rafts over their heads. They lay in the surf while waves pounded them, swam relay races, climbed walls and ropes and raced in the deep sand of Coronado's beaches. And they did not sleep.

On the second night, Cleveland, a Navy airman apprentice, and the others were ordered into San Diego Bay. Cleveland, 22, remembered the hypothermia and panicked.

For almost 20 minutes, the fully clothed men swam. As instructed, they removed their boots and socks in the water and tied them around their necks.

They were ordered back to the steel pier, where they lay on the cold metal. An instructor hosed the men down with bay water as they did push-ups.

"Keeps them from overheating," the instructor said sarcastically.

Kenneth Graham, a Navy petty officer second class, confessed that he had lost one of his boots in the bay. The group returned to the water, diving until they found it. Cleveland's face was pinched in fear.

"It was the cold," the Oklahoma native said later. "And the night. . . . The dark has a way of taking things away. . . . I was petrified."

For the chance to belong to the military's most elite special operation force (see accompanying story), Cleveland and 57 others were going through what is widely regarded as the toughest military training in the United States. The program is so strenuous that only half of those who enroll will graduate and become SEALs, sea-air-land commandos.

The most intense part of the 25-week training is Hell Week, a name that evolved over 47 years from its original name, "Motivation Week."

During Hell Week, the recruits are almost constantly wet and cold. They lose their toenails and rub raw huge patches of skin. Their joints swell up like melons. Afraid they will be unable to put their boots back on, they rarely take them off. In the course of the week, the men faint, vomit and hallucinate.

"I just had to suck up pain," said William (B.J.) Whitted, 28, a Virginia Beach resident who went through Hell Week with a stress fracture in each leg. "If you go through Hell Week, you feel a sense of superiority. You have done something few people could tolerate."