This image, by Robert de Gast, shows a patent tonger off Chesapeake Beach with four skipjacks in the background. It was taken on a "warm winter day" in 1970, Mr. de Gast noted. (Robert de Gast)

Robert de Gast, a photographer whose 1970 book “The Oystermen of the Chesapeake” captured in harsh and unsentimental images the final days of America’s last fishing fleet under sail and is regarded as one of the finest depictions of the watermen who make their living there, died Jan. 3 at a hospice center in Baltimore. He was 79.

The cause was cancer, said a daughter, Sabrina Glaeser.

Dutch by birth, Mr. de Gast spent most of his life as a freelance photojournalist and commercial photographer on the shores of the Chesapeake Bay. He wrote and illustrated a half-dozen books, including one about the bay’s lighthouses and two about cruising its tributaries. His best-known was his first.

Paula J. Johnson, a curator at the National Museum of American History’s work and industry division, called “Oystermen of the Chesapeake” “a masterpiece among volumes devoted to the bay and its people. It’s not a romanticized look at the work. It builds a more nuanced, more atmospheric portrait. It gives a sense of place before the phrase ‘sense of place’ became fashionable.”

In the late 1960s, Mr. de Gast spent a year with dredgers and tongers on both sides of the bay. The annual oyster harvest was about 3 million bushels, compared with a little over 1 million now. Among the more than 3,000 work boats were 39 skipjacks, beamy shallow-draft wooden sailboats, most in poor repair and with an average age of 53 years.

This image is captioned "Soon or late, ain't gonna be neither shuckers left." It shows a lone worker picking up oyster shells at McNasby's oyster house in Annapolis in 1970. (Robert de Gast)

In his black-and-white pictures, Mr. de Gast depicted the winter fishing season in stark terms. Decks are piled high with what looks more like ore than living things. Huge, dirty sails luff in becalmed creeks. Bleached, abandoned boats rot at the end of tidal guts.

The white and black faces of the oystermen are rarely legible and almost never face the camera. Instead, the portraits are of the moments and objects. A view below-decks where two men, hands to their foreheads, pray before eating. A hand with cracked fingernails on the spoke of a ship’s wheel. A fistful of large-denomination bills on payday.

“It was all done without really any conversation,” Mr. de Gast recalled recently. “I had four cameras strapped to my body. I was dressed accordingly. I never asked them for anything. It was like a play.”

The book’s format was horizontal with liberal use of white space that emphasized the flatness and wideness of the bay. Four essays by Mr. de Gast were at the back of the book. The only text in the photographic section were anonymous quotes that caught the outlook and dialect of the oystermen: “Arsters look thicker than either year yet”; “It ain’t no wind, but it’s a fair wind”; “I’d been hopin’ to find me a rank patch.”

Three thousand copies of “The Oystermen of the Chesapeake” were printed by International Marine Publishing Co. It took several years to sell them all.

In a review in 1971, the New York Times called Mr. de Gast’s approach “perfectly clear and straightforward” and noted that “to focus on such an archaic occupation is to induce in the urban viewer a foolish nostalgia for a life he never knew and could never endure.”

Robert de Gast was born in The Hague on Oct. 10, 1936. His father, who built pianos, resettled the family in Linden, N.J., when Robert was in his teens. To improve his English and declare his independence, he worked on a cattle ranch in Oklahoma for a year. In 1954, he enlisted in the Army and was trained as a photographer.

Over the years, he took pictures for magazines including National Geographic, Sail and Proceedings Magazine, the U.S. Naval Institute publication.

His books included “The Lighthouses of the Chesapeake” (1973); “Western Wind, Eastern Shore: A Sailing Cruise Around the Eastern Shore of Maryland, Delaware and Virginia” (1975); “Five Fair Rivers: Sailing the James, York, Rappahannock, Potomac, and Patuxent” (1995); “Unreal Estate” (1993), about abandoned buildings on Virginia’s Eastern Shore; and four volumes about San Miguel de Allende, a city in central Mexico where he lived for two decades before returning to Maryland about three years ago.

His first marriage, to Anja van Rijn, ended in divorce. Survivors include his wife of 48 years, the former Evelyn Chisolm, and three children from his first marriage, Sabrina Glaeser, Makaria Jayne and Justin de Gast, all of Annapolis; two sisters; and four grandchildren.

Mr. de Gast enjoyed recalling a memorable assignment as a private first-class Army photographer.

He was sent to Fort Meade, Md., to photograph President Dwight D. Eisenhower and Gen. Omar Bradley before the two military eminences played a round of golf. They posed without instruction. Mr. de Gast took one exposure, the flashbulb firing.

“Aren’t you going to take another picture? Everyone for the last 30 years has always taken two pictures,” Bradley asked.

“General, I think I’ve got it,” Mr. de Gast answered. “And he looked at me and said, ‘Son, you’re going to go places.’ ”

That would be a good end to the story, but it isn’t the real end. To take another picture with the 4x5 Speed Graphic he was using, Mr. de Gast would have had to pull a film cassette out of the back of the camera, turn it over, and put it back in.

“My hands were shaking so much there was no way I could have done that,” he said.

David Brown is a former Washington Post staff writer.