You are in a damp, cold tunnel that stretches five-eighths of a mile before it ends in eerie darkness. What little light there is comes from dim illuminated yard markers 20 feet up on brown, sweaty walls.

Steaked high against the walls are the gray hulls of miniature battleships, torpedoes and submarines. The click of your footsteps echoes endlessly down the tunnel. To your right is a deep canal, maybe 15 yards across, then a ledge, then another , shallower canal.

From the end of the tunnel comes a great mechanical clanging and hooting, lights appear, thereis the noise of big machinery on the move. On the far canal you see a couple hundred tons of steel gadgetry roaring up a pair of rails at 15 miles an hour, pushing a model destroyer 10 feet long.

From just below, in the near canal, you are startled by a voice. There is a woman in a Kayak; she has paddled up next to you in silence.

"God," she says. "I feel like I'm in a James Bond movie."

Welcome to the nightly pracitce sessions of the Washington area's world-class kayak and canoe paddlers, a couple dozen young athletes who are pointing toward gold medals in 1979 by sweating out their evenings in 1978.

Last year at the biennial world championships in Spittal, Austria, the U.S. team placed third overall. Forty percent of the paddlers on the U.S. team were from the Washington area.

A lot of that, according to coach Bill Endicott, has to do with the fact that in the 1930s the government kept people from starving by putting them to work on public works projects.

One such project was the Navy's David Taylor model boat basin off MacArthur Boulevard just outside the Beltway. All day long the Navy and private boatbuilders use the huge bathtubs to find out what will float; at night, Endicott and his charges use them to find out what they need to do to win gold.

It is, according to Endicott, "the best winter paddling anyone's got in the world. All the other paddlers can do is lift weights and run. We almost have an extra season."

The Taylor basin is one factor contributing to Washington's emergence as a national hotspot for training whitewater racers.

The capital has an extremely active club structure to back Endicott and his students-the huge Canoe Association. And it has excellent outdoor facilities. "There are perfect rapids up the Potomac just below Great Falls," Endicott said, and a good summer flatwater training area in the feeder canal below Brookmont Dam.

The upshot of all this is that Endicott, one of six regional coaches for the U.S. national team, has been getting calls from paddlers in California, Texas, Massachusetts and elsewhere around the nation.

"They want to move here to train for the worlds in 1979," said Endicott.

Endicott and other Washingtonians will have a chance to compare some of these supplicants and area whitewater speedsters in two days of championship races on the Potomac over Easter weekend, March 25-26.

Races start both days at 10 a.m. and good vantage points are available on both sides of the river by walking a short way downstream from the Great Falls parks.

Some local racers to watch are Bobby Robinson, 16, who became the youngest American world medalist ever when he took a bronze at Spittal last year, John Lugbill, a high school football player with a barrel chest as big as Ron McDole's; David Hearn, Ken Ford and Paul Flack.

"Any of those guys could win us a gold medal in 1979," said veteran paddler John Stuart.

But what price glory?

Even the Taylor basin's own public relations specialist admits that the huge testing pools, where lights are kept to a minimum to keep the algae down, would make "a nice place for a murder."

But the youngsters keep coming back, night after night, to be sent off in windsprint waves by Endicott's countdowns, to battle the slalom gates while the coach runs alongside, cajoling and criticizing.

Said Stuart, who at 27 is trying to get back in shape for competition after a layoff, "There's only one thing you have to accept when you take up this sport-there are no shortcuts."

The basin gives Washington paddlers a three-month-a-year edge over the rest of the world, and they're using every bit of it.