The artist Winslow Homer was the Ishmael of painters.

Water was his element. On this, the 150th anniversary of his birth, astrologers and seafarers might note that he was born beneath a water sign, that of Pisces or the fish. Homer needed oceans, or lakes or swamps or rivers, the way other men need women. He was a solitary wanderer, a stubborn sea-struck man.

Homer (1836-1910) sailed with the herring fleets to the gray banks of Newfoundland, with sponge divers off Nassau, and in Cuba and Key West. Homer knew by heart the piled clouds that rise above the Gulf Stream, and the amazingly blue waters that begin just beyond, calm Adirondack lakes, cold Canadian rivers and West Indian lagoons. Homer disliked strangers, cities and the arty. He filled his pictures with boats of all descriptions, catboats, lifeboats, sloops, long birch-bark canoes. Even when confined to land, he chose to live alone -- at Prout's Neck on the coast of Maine -- within sight of the sea.

No American has ever done such watercolor paintings. John Singer Sargent's, next to his, seem facile and French, and Whistler's seem tepid, and Demuth's almost prissy. Even Homer's oils appear ponderous and dim when glimpsed beside his colorful, sun-bright works on paper, 99 of which go on public view this morning on the ground floor of the West Building of the National Gallery of Art.

He said, "You will see, in the future I will live by my watercolors."

Water's glints and water's sounds -- the whirring whine of fishing line tearing through the reel, the slap of waves on wooden hulls, the creak of wind-taut rigging, roaring rapids, gulls -- fill his exhibition. The light levels are low, for watercolors fade, but still these pictures glow. The sunny ones are blinding. Even those that show the blackness of the mangrove swamps, or nighttime on the lakes, or North Atlantic mists, shine like movies in the dark.

The National Gallery of Art is these days on a tear. "The Treasure Houses of Britain" will be there through April 13, its grand Impressionist exhibition will run through April 6, its Ansel Adams show just closed. Perhaps it is no wonder that 220,000 visitors were counted at its doors on a recent three-day weekend. That trio of exhibits perfectly triangulates the Winslow Homer show.

Homer loved the sea as much as Adams loved the mountains, and both of them were willing to lend an audience-pleasing, even melodramatic beauty to the hardly-touched-by-man scenes that they sold with much success. Both men worshiped light, and fact, and the rightness of exactitude. Homer was as careful with drawing-in-perspective as Adams was with printing. Both out-of-doors photography and watercolor painting demand patient waiting for precisely the right moment, the right weather, the right light -- but that waiting is then followed by a Zen-like burst of action. The shutter clicks, the wet brush flies. Watercolor painting requires speed and dash; mistakes can't be corrected; one splash, one drip, one awkward bleed, and the entire sheet is ruined. Homer's watercolors have an almost photographic attitude toward time.

The British country house show casts another light on Homer's exhibition. Though he did not care for horses, Homer in his own way was as keen for blood sport as any English squire. His earliest known drawing, sketched on the end-paper of his copy of "Boy's Treasury of Sports, Pastimes and Recreations," shows a lone man fishing. It was a pastime he'd return to throughout his long life.

In 1886, he became a charter member of the North Woods Club, a hunting and fishing preserve on Mink Pond in the Adirondacks, and also of the Tourilli Fish and Game Club, a 355-square-mile spread of northern Quebec wilderness that "suits me," he once said, "as if it was made for me by a kind of providence." He also fished with much delight as well in England and Key West and in Homosassa, Fla.

Almost all his watercolors were painted on the spot while on such art-and-sport vacations. The few humans who appear in Homer's later pictures are all intent on killing shark or trout or game. The point of view that he preferred is one that puts the observer at the center of the action, inches from that leaping trout or that wild-eyed drowning deer. The beautiful-and-horrible moment between life and death is central to the power of Homer's art.

While Homer's dogs, dying deer, fishing rods and fresh-killed trout evoke the fox hounds and the stags of the British exhibition, his colors call to mind those of the Impressionists now displayed upstairs.

For though he had no interest in ballet dancers, cafe's or the railways of Paris, Homer, like the Impressionists, also turned away from the licked-and-polished look of academic painting, and painted en plein air, and improvised his brushwork, and put his brilliant colors down rapidly and lightly one color at a time.

Yale's Helen A. Cooper, who organized this show, has filled its walls with those rare pictures not yet bleached by light. Their colors are, in consequence, her show's great revelation. Homer, Henry James observed, "naturally sees everything at one with its envelope of light and air." The colors of these paintings glow like stained glass against sun.

Homer, like Seurat, was a theorizer of color. He owned a copy of Michel E.Chevreul's "The Laws and Contrasts of Color" (1859), and studied it with care. He was comparably attentive to Ogden N. Rood's "Modern Chromatics" (1880). Homer's paintings are so lifelike that one tends to overlook how much their light relies on complementary colors. Look, for instance, at the way the red sleeves of "The Woodcutter" (1891) shine against that slate-gray sky, or at the way that lemon-yellow wall of "Flower Garden and Bungalow, Bermuda" (1899) contrasts with the varied blues of the sea and sky.

Homer rarely spoke of art, but he did once say: "You can't get along without a knowledge of the principles and rules governing the influence of one color upon another. A mechanic might as well try to get along without tools."

"If this country has contributed anything distinctive to the craft traditions of painting," observes Clement Greenberg, "it is in the watercolor style that Homer founded."

Homer started as an illustrator, almost a reporter, working as a free-lancer for Harper's Weekly, Hearth and Home, and other publications. He covered Lincoln's inaugural in 1861, and then the Civil War. And his paintings tell us stories.

A grizzled Adirondack woodcutter, his clothes the color of old bark, strokes a giant, dying tree in the 1894 picture Homer called "Old Friends." In "After the Hurricane" (1899), a shipwrecked sailor sleeps exhausted on a wave-washed beach beside the bit of wreckage that saved him from the sea. We have seen that man before -- in "The Gulf Stream" (1889) -- patiently awaiting death on his dismasted schooner in wild, shark-infested seas. Often in this show we read the images in sequence: a boat-borne pack of hunting dogs waits to be released; a hounded stag bursts through the wood and plunges into water; a puff of smoke, a fatal shot, and then we see the hunters. The dead deer now is in their boat, the hunting dogs retrieved.

Those hunting pictures call to mind a Hemingway short story: Strong men without women confront death in the woods. The air is crisp, the water cold, and a certain awkward distance, part silence and part unnamed grief, divides the protagonists.

The barefoot and straw-hatted boys who go about their business in such early pictures here as "Three Boys on the Shore," "Watching the Harbor" and "Waiting for the Boats" (all 1873) are the eastern seaboard cousins of Tom Sawyer and Huck Finn.

Homer never married. For a while in the mid-1870s he lovingly portrayed an unsmiling red-haired woman. In "Portrait of a Lady" (1875), she pricks her finger on a rose thorn. In one of the best pictures here, "The New Novel" (1877), she is reading on the grass. In "Girl Seated" (1879), she holds an open letter; what it says we do not know. In "The Trysting Place" (1875), she is waiting in the shadowed woods. Her lover does not come. Those pictures seen together suggest some subtle, sad romance.

The other women appearing in these pictures, especially the fisherwomen he portrayed in the early 1880s while at Cullercoats in England, are somehow unconvincing. They are a little bit too brave. Standing boldly by the icy sea with their skirts wind-whipped about them, they uncannily resemble the heroines of the working class who strike such noble poses in socialist-realist art.

A strange sense of aloneness haunts many of these pictures. The few people they portray somehow fail to make contact. Homer, at Prout's Neck, was as much at ease with solitude as Thoreau at Walden Pond.

Homer was a loner, and the viewer who explores his art -- who sees the black bass jumping, and the puma in the trees, the dead tree on the hillside or the storm-tossed boat at sea -- becomes a loner, too.

And yet there is within this art a deep strain of affection. The breeze that bends the palms, the sun on white-hulled boats, the always-shifting sky are more than seen. They're examined with an almost sensual sensitivity.

Homer, at Prout's Neck, rarely welcomed visitors. Often when he painted there he'd put up a large sign, "SNAKES AND MICE," to keep passers-by away. But he sometimes made exceptions. Once he took Charles Hopkinson, the painter, on a drive through the main countryside. Then Homer left him at the cart, while he walked toward a swamp carrying a batch of watercolors and sketches. Fifteen minutes later, Homer returned without them. "There," he said. "I feel much better."

Of course he must have edited. Not even Homer could have constantly maintained the remarkably high standards achieved by the pictures here on view. Still, he left nearly 700 watercolors. Of those that have survived intact, Cooper has selected many of the best. A $450,000 grant from IBM helped pay for her thoroughly researched, cleanly written catalogue, and for the exhibition's tour. "Winslow Homer Watercolors" will travel to Fort Worth and New Haven, Conn., after closing here on May 11.