A silent sentry of the shipping lanes, it sits only 1 1/2 miles offshore and seven miles south of the Chesapeake Bay Bridge. But the white frame Thomas Point lighthouse seems as remote an outpost as can be found on these estuarine waters.

No telephone links it to the mainland, just a ship-to-shore marine radio that doesn't work very well and a feeble CB radio that is better than nothing. Coast Guard crew members assigned here say they live for the biweekly mail delivery.

This is the last staffed lighthouse on the Chesapeake itself; the Coast Guard mans one other onshore at Cove Point in St. Mary's County..

But at Thomas Point, these are the twilight months: As the sun sets beyond the western shore, it is also setting on Coast Guard duty at the lighthouse, one of only 35 in the United States still staffed. Come summer, officials say, the Thomas Point lighthouse crew will go ashore forever.

With new technology on board, the lighthouse, built in 1875, will run itself. Only an occasional maintenance man will climb the hexagonal structure that sits on pilings above the water.

That nobody will live here and few will visit has, ironically, given new urgency to an old mission. Boatswain's Mate First Class Frank Remaly, in command of what is officially called the Thomas Point Shoal Light Station, is determined to leave the place freshly scrubbed and painted.

"Overall objective is to have the entire interior of building repainted prior to May 1986, or prior to automation date," states Remaly's memo on the kitchen bulletin board. "A reduction in liberty may result should automation date be advanced. The building will be repainted prior to closing."

Despite his determination to repaint everything in sight, Remaly thinks having government employes at the lighthouse is a waste of taxpayers' money.

For now, four men are assigned to the post, usually two at one time. They work 12-hour shifts, two weeks on the lighthouse, then two weeks off.

"The first couple of nights, you sleep six to eight hours, then you sleep 12 hours," Remaly said. "Then, the last couple of nights, you can't sleep because you've slept too much. You go ashore, it really goofs you up; your girlfriend or wife gets up at 8 a.m. You bounce between these two life styles. It's really rough on you."

But when they aren't sleeping or painting, there's isn't much to do. For several months, water and air temperatures and wind direction and velocity data have been automatically collected and sent by satellite to the National Oceanic and Atmospheric Administration weather center in Texas.

The men still broadcast daily water temperatures to the Annapolis Coast Guard station at Thomas Point so that information about ice conditions is readily available in wintertime.

They also make sure the light flashes every six seconds, and, in daytime, they "secure" the light, which is to say they turn it off.

When visibility is five miles or less, they turn on the foghorn, which sounds four times a minute and can be heard for five miles.

"You don't sleep for the first day when it's on," said Remaly. "It takes a long time to sleep, then you just toss and turn. We all wear foam earplugs."

When the men are up and about, they pass the time building ship models, reading -- the small library includes "Chesapeake," "A Bridge Too Far" and "Jaws" -- watching movies with a videocassette recorder, writing letters and watching television.

Reception is good here, they say. The television pulls in stations from Washington, Baltimore, Salisbury, Md., and sometimes New York. As for radio, said Seaman Dennis Schuman, "You click it on, you get DC 101, 98 Rock -- everything."

Schuman brings his VCR. Scott Metzbauer, a machinist technician 2nd class, brings the tapes.

"He's a 'Rambo' fanatic," Schuman said. "We watch adventure movies, but no love stories. We don't want to have anything to do with girls for two weeks . . . .

"The only thing I pray for is to get mail out here," he added. "If you don't get mail out here, you go crazy."

There is another way of looking at life in the middle of the bay. "This is nice and slow out here -- mellow," Remaly said. "You get ashore, everybody's in such a rush."

Remaly, 40, joined the Coast Guard in 1963 "just to get out of the Pennsylvania coal region." He lives in Burlington, Ontario, and commutes back and forth for his two-week shifts.

The best time to be at the lighthouse, all hands agree, is summer. By day the men use government-issue binoculars to watch bikini clad -- and unclad -- women on passing sailboats, and by night they use nets to catch crabs from the two rock piles that undergird and protect the structure.

Holidays can be hard, the men say. Remaly spent Christmas here, Schuman New Year's Eve. "Just thinking about all the partying people were doing and watching it on TV made me sick," Schuman said.

Wintertime, and the ice it brings, can be fearsome. An arrow-shaped ice guard sits on the north side of the property to break the packs of ice that float down the bay from the Susquehanna River. Without the ice guard, the Coast Guard men say, the lighthouse would be smashed to pieces.

"When the ice is moving around here, you can't sleep," Remaly said. "The whole building shudders. Ice'll climb up the side of the light, level with the railings, 15 feet above the water level."

Last winter, ice in the bay was two feet thick and "as far as you could see," Remaly said. With the 41-foot Coast Guard cutter frozen in, he said, a state ice-breaking tug was used to make the biweekly crew change.

But despite the recent cold snap, it's been too warm for ice on the bay this winter, and only the rocks below the lighthouse have been glazed.

The lighthouse crew was evacuated once during a severe storm in November. But other than the running aground of a 668-foot freighter just south of the station, there's been little excitement and lots of spare time at the Thomas Point lighthouse this season.

The other evening, Schuman went on duty at midnight, recorded the air and water temperatures, cleaned up a bit, typed a couple of letters and then, from 2:40 to 5:15 a.m., watched a telecast of "Beyond Victory," a 1931 movie about why soldiers enlisted in World War I.

The lighthouse operates as a Coast Guard unit apart from the main station at Thomas Point, but the two depend on each other in sometimes surprising ways. Talking to the base over the CB, Remaly said, "If anyone is going uptown today, have them pick me up a pack of Winstons or two or three, would you?"

In return, the lighthouse supplied the main Coast Guard station that day with a case of paper towels. "The federal supply system is kind of strange," Remaly said.

This lighthouse-to-shore trading, however, will end soon enough.

Beyond such mundane matters, there is concern about the survival of the unguarded lighthouse once it's left on its own. Of 74 lighthouses that once graced the bay, only 32 still stand, and many of them have been vandalized.

"After what I've seen happen to other lighthouses, I just hate to leave this place," said Schuman, who is bound for Coast Guard storekeepers school in Petaluma, Calif.

"I'll miss it," he said. "I'll miss it."

"It's not bad duty out here," he said, while the program "Good Times" played on the lighthouse television. "It's not bad at all."