Michael Cummings said he was sure he had made his last mistake. "I knew I was going to drown," he said. "We were both done for."

But as Cummings, 61, and his wife Polly, 60, were going down for the last time Prince George's County Police Officer Robert F. Derfler swam to the rescue.

Derfler was just doing his job - helping people in distress, except for one thing: the incident took place last Saturday in Nag's Head, N.C., where Derfler had gone on vacation.

"My wife and I had been swimming in the surf near the beach," said Cummings, who works for the telephone company in Richmond. "She got caught in a riptide going out. When I went to help her I got caught too. We both know the water and it was a silly mistake to make. If Bob hadn't been alert, it would have been my last one."

Derfler, 31, an officer for eight years who works on the sex squad, noticed the two struggling in the water as he walked along the beach.

According to Cummings, Derfler grabbed a raft and swam to them. "He got my wife in the raft and onto shore but by the time he got back for me we were a quarter mile out and he was tired from fighting the waves.

"We couldn't get back in at that point so we just hung onto the raft and hoped."

They hung on and hoped for almost an hour. Finally a Coast Guard cutter, sent out after Polly Cummings rushed into her cottage and called for help, arrived and pulled the two exhausted men aboard.

"Bob told me later that he'd been working out the last couple weeks because he's gotten out of shape eating his new wife's cooking," Cummings said. "If he hadn't done that, we'd both have been done for."

The Coast Guard also reported that the previous day Derfler had pulled two struggling 16-year-olds from the water in a similar incident.