It's been 25 years since I first laid eyes on waterman Jackie Russell. Back then he was overseeing construction of his new skipjack and prospects were bright as he prepared to grab his share of the Chesapeake's abundance.

Russell's snow-white Dee of St. Mary's was soon launched and he set to work with a crew dredging oysters under sail, as Marylanders have done for hundreds of years. He was not disappointed. He remembers hauling up 50 bushels of oysters an hour in the early 1980s.

Nor was it only shellfish he captured. "He'd come back with that boat piled high," says his wife, Viki Volk-Russell. "I'd just moved here from Colorado. I took one look and asked, 'Who is that man?' Somebody said, 'It's a sad story, he's just been divorced.' I said, 'Oh, what a shame!' "

Time has been kind to the Russells. They have two teenage daughters, a rambling old waterfront house the evening sea breeze cools and a going business. But the seafood trade he built on the health and abundance of the Chesapeake has taken a sharp turn for the worse.

These days the Russells run Chesapeake Bay Field Lab, a nonprofit educational operation designed to show folks what the bay was like not so long ago and what we all hope, perhaps foolishly, it could be again. As for oysters, they're just about gone.

As recently as 20 years ago, Maryland measured its oyster catch in the millions of bushels. Last year it was just 23,165 bushels, almost all planted by the state in a put-and-take operation Russell describes as "going through the motions of trying to keep a dead fishery alive."

It's in the nature of fishermen to be optimistic and Russell remains so. He points to a pocket of plump oysters nearing maturity in the nearby St. Mary's River as a sign things could turn around, and he still tends 25 or 30 crab pots on summer mornings. Working the water is "like a virus or a fungus or something," he says. "When you get it in your blood, you can't shake it out."

But most of his work from March to November is aboard the Dee, which he transformed from working dredge boat to classroom when the oysters gave out. Day in and day out, Russell greets busloads of youngsters from schools and camps around the region who come to this low-lying island at the mouth of the Potomac to learn of the declining wonders of the Chesapeake.

"If you can't hold it in your hands," says Russell, "you won't take care of it. We're trying to take this culture we're so rapidly losing and carry it into the next generation of kids."

Oystering began its slide in the late 1980s with the arrival in the bay of a pair of lethal parasites, MSX and dermo. "By 1989 we were down to catching 25 bushels a day, working from sun to sun," said Russell. "It took all the fun and nostalgia out of it."

The decline was helped along by overfishing, pollution and algae blooms that robbed the water of oxygen. Like all environmental problems, the loss of oysters had repercussions. As they disappeared, the bivalves took with them their role as filter feeders removing nutrients from the water, and the bay got murkier even faster.

Russell saw the writing on the wall in the late 1980s and began running educational trips for the Chesapeake Bay Foundation, the multimillion-dollar environmental organization based in Annapolis. When CBF cut funding, he formed his own nonprofit and has been plugging away ever since on a modest budget of $100,000 or so a year.

Last week I joined two classes of fifth-graders from Arlington's Ashlawn Elementary School for a day on the Dee. "This is the best field trip we do," said teacher Susan Hodgkins. "Capt. Jack fascinates the kids. The first question we get when school opens in September is, 'When's the skipjack trip?' "

"It's so different from our regular environment," said her colleague Jimsey Frye. "Our kids think of fish as fish sticks and water as what comes from the faucet."

If you think city kids can't appreciate the natural world, you need to spend a morning on the Dee, where we watched a 10-year-old girl plant a kiss on a half-rotten menhaden before stuffing it into a crab pot for bait, saw boys and girls elbow each other for the chance to slurp an oyster off a shell and watched kids and teachers alike light up with interest as they hoisted an oyster dredge or crab pot from the bottom and pored through the muck for amphipods, peeler crabs, shells, mussels, oysters, worms and other icky critters.

"Once," said Russell to raise the bar, "I found a wallet with a $50 bill in it."

The kids from Ashlawn Elementary found no money but they did get to see and touch eels, diamondback terrapins, mud crabs, oyster toadfish, bull minnows and flounders. They learned to hold a feisty blue crab so it couldn't nip their flesh. Fifty youngsters learned to tie a bowline knot, though probably not one remembers how today. They yanked each other across the grassy parking lot in a tug of war, dug up oysters with shaft tongs and stuck their fingers in a bucket of bay water and tasted it, to learn what seven parts per thousand salt water is like.

The bay, of course, is where the salt sea meets freshwater rivers, forming in the mix zone a breeding ground for countless forms of aquatic life. Or did, until man started crowding its shores.

What's left is worth preserving, what's gone is worth restoring.

But how?

"If you put a serious focus on these problems, we probably would have solved them by now," says Russell. "We put a man on the moon; we put a camera on Mars."

Russell hopes by putting a little piece of the Bay in people's hands, they'll appreciate it and want to preserve it. "Every child that gets in a car, you don't have to tell them to put on a seatbelt. If we could do the same thing with the bay . . . "

Chesapeake Bay Field Lab offers group environmental field trips on the Dee of St. Mary's all summer. Four times a season, starting June 27, it also has onboard feasts of all-you-can-eat crabs, corn, tomatoes and cantaloupes. Call 301-994-2245 or check the Web site, www.thebaylab.org.

"We're trying to take this culture we're so rapidly losing and carry it into the next generation of kids," says Jackie Russell, with fifth-graders from Ashlawn Elementary School in Arlington.