Walter L. Mess, an American spy who captained a speedboat that ferried agents to and from secret missions in the China-Burma-India theater of World War II, died May 26 at the Hermitage nursing home in Alexandria. He was 98.

The cause was end-stage chronic renal failure, said his son, Walter Mess Jr.

Mr. Mess, who kept mum about his wartime experiences until the 1990s, was better-known to the public for his nearly 30 years as chairman of the Northern Virginia Regional Park Authority.

Under his watch — he stepped down in 2004 — the park authority developed the 45-mile Washington & Old Dominion trail, acquired the 5,000-acre Occoquan Reservoir shoreline and preserved more than 10,000 acres.

He was a founding member of the authority, established in 1959, and his vision for the organization dated to a wartime visit to San Diego, where he saw a free regional system of parks, golf courses and swimming pools.

Walter L. Mess, an American spy who ferried agents to and from their secret missions in the China-Burma-India theater of World War II in a speedboat he built himself, died May 26 at a nursing home in Alexandria. He was 98. The crew of OSS Maritime Unit, boat P-564: Back row, from left: M/Sgt Ear L. Williams, Cpl. Joseph P. Jones, S/Sgt. Lester H. Linville, T/5 Joseph E. Viola. Front row, from left, Sgt. Willard R. Floyd, T/Sgt Harry F. Johnson, 2nd Lt. John A Swayze, 1st Lt. Walter L. Mess (Skipper), WOJG James H. Flynn (First Mate), Sgt Benjamin W. Brunaugh, T/Sgt Lous K. Woodland and Cpl Robert L. Philpott. (USASOC History Office)

He had been an outdoors enthusiast since his childhood in Alexandria, accompanying his father and uncle on boating and hunting expeditions.

During World War II, he was recruited to the Office of Strategic Services, a forerunner of the CIA, based in large part on his boating skills. He served in a maritime unit that performed clandestine missions in enemy waters — a model for the Navy Seals of later decades.

The OSS had sent Mr. Mess to Burma by 1944, and he was among an estimated several hundred skippers who dropped off agents and combat swimmers to gather information about enemy targets in anticipation of larger landings.

“Shooting wasn’t our mission. Our mission was taxi driver, our mission was not to fight, but we were prepared to do it,” Mr. Mess explained to espionage historian Patrick K. O’Donnell.

He told O’Donnell, whose book “Operatives, Spies and Saboteurs” features Mr. Mess, that the boats went 50 to 70 miles up narrow and shallow tributaries, slipping past enemy encampments. He recalled seeing fires set by Japanese soldiers and steering the boat silently past them at night.

He would rendezvous with the U.S. soldiers where he had left them off. “If we were under fire, we would use a bicycle tire to snatch the men,” he said. “They would stick their arms up, and we’d hook them with the bicycle tire and swing them into the boat, using the bicycle tire as a hook.”

Sworn to secrecy, Mr. Mess didn’t tell his wife about his OSS work for decades. “I was told to keep my mouth shut,” Mr. Mess told the Falls Church News-Press in 2008. “She was so angry, she didn’t speak to me for a month.”

Walter Lansdale Mess was born in Washington on Dec. 20, 1914. He moved to Alexandria as a child and spent most of his adult life in Falls Church. He graduated in 1933 from St. John’s College High School in Washington and later from George Washington University and Catholic University’s law school.

After the war, he worked in real estate and mortgage lending. He retired in 1983 as senior vice president of the B.F. Saul real estate company.

His wife of 61 years, Jean Ogle Mess, died in 2002. Survivors include four children, Walter Mess Jr. of Keene, N.H., Jean Lewis of Falls Church, Patricia Urick of Sarasota, Fla., and Margaret Vidumsky of Chadds Ford, Pa.; 11 grandchildren; and 20 great-grandchildren.

A half-century after his wartime service, Mr. Mess reportedly received an honorary green beret for his contributions to military intelligence.

“Somewhere along the way, I got some Bronze Stars and a lot of other fancy things, but none of that really matters,” Mr. Mess told the Washington Times in 2007. “I had a good time. The reason I had a good time was because I lived on the edge for a while. I was not young when I left for the war, I was 28. I got lucky — I survived.”