TOY BOATS sail in and out of dreams wafted on the waves of sleep.

Other voyages are not so smooth.

In the pond, toy boats face new perils. Diabolical pirates board your boat to do you the dirty. The waves caused by the launching of other ships threaten to capsize your brave boat. Other boats, not so well captain'd motor right into your innocent ship. Seafarin' dogs, under the mistaken impression that ships are edible, capture boats in their mouths and run away with them. And always, there are the boats, worn out with their adventures, that mysteriously sink in the middle of the deep.

At the seashore, when the sun is high and your shovel strong, you can make small tidal ponds in the sand, ringed with castles, entered by drawbridges, crossed by locks. If you have enough peanut butter and jelly sandwiches, and the adults have enough mystery stories, you can play for hours. But don't go down the beach in search of shells, because the tide might turn and your boat would go out to sea, lost forever in some Devil's Triangle.

With all the perils, it's surprising that any toy boat ever came to safe port. The best toy boats, tin and cast iron, were manufactured only between 1870 and 1955, almost all in Germany and France. For the past quarter of a century or so, children (and their doting parents) have had to struggle along with the inferior plastic boats or an occasional handmade wooden ship produced by a superior grandfather.

These 25 years have also seen the sad decline of real boats -- the dry-docking of ocean liners, sunk by the airplane, and the de-emphasis of the man-o'-war. But today, when pleasure boats are more numerous than ever, ship cruises are sold out, and airplane travel has lost its novelty, there is considerable interest again in tales of the deep.

A flotilla of what's left of the great toy boat armada, 1870-1955, is sailing at the National Geographic Society's Explorers Hall from Thursday through the end of the year. The boats are the Geographic's traditional Christmas show, installed by curator Peter Purpura.

The 200 boats -- worth somewhere around $250,000 -- were collected by Robert Forbes and his father Malcolm Forbes. The elder Forbes, owner of the business magazine, has a collection of everything, from Faberge objets d'art to transoceanic balloons to toy soldiers, defending the Forbes offices overlooking the Straits of Gibraltar.

The breadth of Forbes' interests can be judged by his two recent purchases -- the log of Paul Revere's ride and the log of the Enola Gay.

"Toy Boats, 1870-1955, A Pictorial History," documenting, or rather, celebrating the collection by toy expert Jacques Milet and photographer Robert Forbes, has just been published by Scribners.

The flagship of the fleet is a solid silver paddle steamer, made in 1913 by Faberge as a present to Alexis, the only son of Czar Nicholas. The boat is valued at $65,000. Robert Forbes admitted that even he has never had the nerve to see if it will float. It sails brightly (battery lights) and merrily on dry land while playing "Sailing Down the Volga" and "God Save the Czar." The Faberge boat was the centerpiece during the launching of the book on a dinner cruise around New York Harbor aboard Forbes's yacht, The Highlander.

Young Forbes and Peter Purpura did roll up their trousers and putter around with a few boats in the National Geographic's globe pool in Explorers Hall the other day, to the great glee of visiting children.

At lunch in one of the National Geographic's posh dining rooms overlooking the city, the centerpiece was an 1895 30-inch tin frigate, made by Marklin. You'd expect Burt Lancaster as the Crimson Pirate to come swinging down from its masts any minute. Robert Forbes, over a sherry from Geographic's Paul Sampson's own collection, said he'd turned down $10,000 for the frigate. "Toy boats are much more expensive to collect than trains. It's because trains are still being manufactured, and, well, so many toy boats sank."

A submarine owned by the gardener's son was fished out of billionaire Henry Clay Frick's lilypond in New York many years later -- and promptly purchased by Forbes.

Robert Forbes cames by his fondness for boats when he was 9. His father started the boat collection then -- and remodeled Robert's room with bunks and brass fittings. A great 1956 painting by John Koch shows the Forbes parents and five Forbes boys in sailor suits on their slate terrace. Robert is the one launching the boat in the swimming pool.

"I was heavy into boats," said Robert, "until I got my first Bb gun. Do you know how long it takes to sink a toy boat with a Bb gun?"

His father, who went to Europe many summers with his parents, writes in the book's foreword that he once took along a toy boat "and with my brothers' aid lowered it -- secured by a strong twine -- the long way from rail to sea. . . . It survived departure from the dock, but within a few minutes of our being underway the bashing soon saw it underway to Davey Jones' locker."

With such antics, it is even more marvelous to see what's left. There's a boat that comes complete with the instrument of its own destruction: a torpedo. If your aim is good, the torpedo hits a button, the boat breaks into two pieces and capsizes. An 1880 Radiguet boat has small brass cannons that actually shoot.

Robert Forbes told a story, from the Berliner Tageblatt of December 1913. The kaiser went to a store on the Leipzigerstrasser to see the toys. After he'd approved of the locomotives and the battleships, he asked for the submarines. No submarines. He drew a picture of a toy submarine and ordered them produced instantly.

Sidewheelers, brilliantly painted flower boats, a bank boat, rowboats, ocean liners, warships and speedboats in the show run on batteries, steam, clockwork and nostalgia. CAPTION: Picture 1, From "Toy Boats" -- Charles Scribner's Sons, New York; Picture 2, Curator Peter Purpura (left) and collector Robert Forbes are knee-deep in toy boats at Explorers Hall; Copyright (c) By Joseph H. Bailey, National Geographic Society; Picture 3, Ocean liners on a small scale. From "Toy Boats" by Jacques Milet and Robert Forbes.; Picture 4, Farberge's silver paddlesteamer.; Copyright (c) by H. Peter Curran.