On Saturday morning, when Roger Meredith pulled his 41-foot oyster boat out of Grasonville, a waterside community on Maryland's Eastern Shore, he thought he was beginning a routine three-hour cruise to Little Creek, where oyster beds were still open despite heavy icing on the Chesapeake Bay.

Fourteen hours later, Meredith was crouched in a rescue helicopter, bone-chilled and shivering but still alive after an ordeal that begun when ice locked around his wooden hull.

"They got me just in time," the 42-year-old waterman said yesterday while thawing out in his Grasonville home. "I couldn't have made it until morning. tThe cold was making my blood not right."

The Coast Guard reported ice as thick as three feet covering parts of the Chesapeake Bay yesterday and air temperatures of 21 degrees as the New Year's cold front continued to hang over the East Coast. Meredith's was the third ice-bound boat that rescue units assisted in the past week.

The Coast Guard is requiring that any vessel moving in the bay's northern reaches have a steel hull and meet certain standards for minimum horsepower. For smaller commerical vessels, three cutters ran an ice-breaking conoy down the bay yesterday.

Meredith expected no trouble when he left Kent Narrows at 10:30 Saturday morning because other vessels preceding him had cut a passage through the ice. But the mid-voyage the tides shifted, forcing the sides of the path together. By 12:30 he was locked in.

His vessel was poorly equipped for such as emergency. He had no flare gun and had not replaced a radio that was stolen last fall. The boat's cabin had a stove, but "it was so cold it wasn't doing any good at all," Meredith said. "I could feel the temperature dropping as soon as the sun went down."

There was nothing I could do. I couldn't notify anyone," Meredith said.

For the next 12 hours he tried to keep warm by staying inside the cabin out of the wind and jumping up and down. he considered trying to walk to Parsons Island, only 500 yards away, but feared falling through the thin ice to freeze to death in the water.

Fresh in his mind, he said, was an incident several years ago that cost the lives of six Eastern Shore watermen. Ice-bound, their boat was lifted out of the water at its bow. As the men attempted to chop away the ice imprisoning them, the stern slipped beneath the surface and the boat sank, taking all six men with it.

Meredith survived, he said, because relatives reported him overdue. A search helicopter sent out by Maryland state police spotted his boat several hours later and alerted another helicopter to pick him up. It set down on the stern and took the cold man aboard. He was not hospitalized.

Weather forcasters are predicting continued cold in coming days, assuring that much of the bay will remain iced over. "This is running about average," said a Coast Guard spokesman. "This is not an abnormal amount of ice."