ALICE TOWN, BIMINI -- As summertime comes to the Beltway, the 2,400 residents of Bimini, a dot-on-a-picture-postcard island 800 feet wide and about 4 miles long, are beginning an active, healthy summer, too. Some of them, that is.

Up at Bailey Town, about a mile away from the End Of The World Bar where I write, Tina Thompson helps organize her slow-pitch softball team for their first game against The Enforcers, Bimini's constabulary team led by a tall, rock-hard Brian Moss.

Tina, a 23-year-old Biminian, has been a slow-pitch fan most of her life, and was a first baseman on the Bimini-Berry Island team in the Bahamas Games last year.

Tina's also an instructor at the Bimini All Age and All Welcome Aerobics Class (BAAAWAC), where I indeed found myself welcome. Moving to the rhythm of a Kathy Smith advanced workout tape, a crowd of two plus me worked up a sweat as, less than 100 feet away, the first giant tuna of the season (583 pounds) cruised by Weech's Bimini Dock and Bay View Rooms on a sport fisherman.

Hank "paid it no nevermind," however, because he was dancing. Thirty-five, with a beard, longish blond hair, a pierced ear and a countenance that would remind you of a rakish but urbane pirate, Hank is a fifth-generation Biminian.

Around 1850 his family came here from Key West via the Carolinas and Wales to enter the respectable and robust business of "wrecking." Such salvage work was made possible by the fine shoals that surround Bimini and drew many a ship to grief.

During Prohibition, the Weeches added rum-running to their efforts, another open-air and energetic profession. Rum-running wasn't illegal in the Bahamas, and if you didn't run rum around here, "you weren't no real Biminian," as an old fellow told me.

"But we don't do those things any more," Hank says; "I do aerobics for fun." Though that sounded like a letdown to me, I didn't argue.

He continued to twist his hips as Nowdla Keefe, founder of BAAAWAC, changed the tape. Twenty-five and dramatically beautiful, Nowdla is exceptional for another reason: It's safe to say, she and her sister are the only native Bahamians on this planet who are Eskimos. Or at least 50 percent so.

And what does the founder of the Bimini All Age All Welcome Aerobics Class charge its participants? "Oh, we don't charge for this," Nowdla said with a surprised look. "We have trouble enough getting people to come for free."

Lack of crowds also characterizes the Iron Man Gym here, which is a shame since the gym is fine indeed for a tiny island. Looking like a well-kept one-room schoolhouse, it is open any time you can borrow a key from one of the dozen regular members, or around 4 o'clock island time, which usually means 6-ish. The Iron Man works on the honor system: A friendly sign asks you to register and leave $4 on the shelf if you can spare it. A thoughtfully placed arrow points to a smooth piece of coral to hold your money.

About a half-mile from the gym, sits a man from Washington, D.C., who has vigorously enjoyed the pleasures of Bimini for 43 years, but who has informed me his only exercise this trip is "going to be lifting a good book and a beer."

Cushing Daniel is now 81, the patriarch of a six-generation Washington family that goes back so far their phone number in D.C. once was 80. He and his brother Raleigh, 77, first saw Bimini from the cockpit of a trainer during World War II. "We were always interested in small boats, you see," Cushing says, "and the moment the war broke out, we got in the Navy as quick as we could."

Cushing laughs at the memory, "Of course, we never saw a boat. We were put in flying machines, and Raleigh and I became navigation instructors, flying time and again over this beautiful island at 120 miles an hour. But we wanted to see it at 12 miles an hour."

Which they did, along with exploring the rest of the Bahamas, at war's end. "We bought a 61-foot Stephens," says the third brother, Clarke, 79, "and for three years on-and-off, my wife and child and my brothers and their girlfriends cruised and swam and fished."

And picnicked, many times on the sprawling, six-acre oceanside ruins of the legendary Bimini Rod and Gun Club. "We loved that property," says Cushing, "and eventually bought it from the boxer Gene Tunney and others."

For a year and a half the brothers fixed it up, flying in from time to time on a four-seater seaplane piloted by "Pappy" Chalk himself, the founder of Chalk Airways. Chalk planes still swoop into the Bimini harbor about six times a day.

From 1948 until the present, Daniel House has been the scene of much strenuous and not-so-strenuous activity. "Back then I chased girls and drank; And fished, of course," Raleigh remembers in a very happy voice. "Now, it just seems nice to sit and play with my grandchildren and their friends."

I think Raleigh Daniel has earned a rest, but know he has passed on his love of being outdoors and active to his children. Lee Dettor, Raleigh's daughter, recently brought her five sons and a dozen friends to the island.

A very trim and fit summer blond, Lee Dettor obviously thrives on the energy of her children (or is it the other way around?), and on many a Friday night in Bimini she takes the kids for the big dance at The Compleat Angler, Ernest Hemingway's old hangout (and more recently Gary Hart's).

One of my most pleasant island memories is the sight of Lee Dettor and a son not more than 7 cutting the rug with obvious pleasure and comfort in the midst of 100 happily rowdy sailors and fishermen. Someone called that living life to the brim, didn't they?

What adventuresome and active things are you doing this summer? Why not take up scuba diving? There are dozens of classes starting right now. Look under "Diving Instruction" in the Yellow Pages.

Or why not learn a little about boating and seamanship and one of these days crew your way down to the Bahamas? It's easy to start.

This summer, in several locations, the U.S. Coast Guard Auxiliary and the U.S. Power Squadron are sponsoring three great courses, and you don't have to own a boat: Boating Skills and Seamanship; Sailing and Seamanship, and Advanced Coastal Navigation. Whatever your plans for this summer, make sure you find your own All Age and All Welcome Activity.

Anchors Aweigh If you're interested in learning about boating or navigating, the Boats/US Foundation can provide information on boating course given by the Coast Guard Auxiliary and by the U.S. Power Squadron. In Virginia, call 1-800-245-2628; elsewhere, 1-800-336-2628.