Lefty Kreh, one of the pre-eminent sport fishermen of his time, died on Wednesday at his home in Cockeysville, Maryland, north of Baltimore. He was 93.His granddaughter Sammantha Aus said the cause was congestive heart failure.For a half century, Mr. Kreh, a globe-trotting fisherman, journalist and author, was a colorful and highly influential figure in both freshwater and saltwater fly-fishing. In countless articles and more than 30 books, in videos, on television and at innumerable public appearances, he converted his vast experience into lucid observations and practical advice for anglers at all levels.Mr. Kreh was always willing to re-examine traditional ideas in a sport laden with them. As he said about fly-fishing for trout in his book Advanced Fly Fishing Techniques (1994): "I feel that many people who are not really versed in the sport have either written or spoken about it, and they have attempted to create a concept that this is a very difficult sport to master. That simply isn’t true."While fly angling in freshwater for fish like trout and salmon is an old sport, saltwater fly-fishing is comparatively new, and Mr. Kreh was one of its earliest champions. His book Fly Fishing in Salt Water, which he said he wrote "not to make money, but so I didn’t have to answer so many darn questions," was published in 1974 and remains an essential text.A saltwater fly of Kreh’s design, Lefty’s Deceiver, is used all over the world, and in 1991 the Postal Service put it on a stamp.Mr. Kreh was much in demand as an instructor of fly casting, the easily misperformed skill of unfurling a heavy fishing line to deliver a virtually weightless lure to wary fish. He gave demonstrations to thousands of anglers at his public appearances. Though born left-handed, he could cast with either hand and customarily used his right, which he said was better for teaching right-handed students.Mr. Kreh also fished with Fidel Castro, Ernest Hemingway, Ted Williams, Presidents Jimmy Carter and George H.W. Bush and other celebrities. Another acolyte is Tom Brokaw, the former NBC News anchor and an avid fisherman. Brokaw said in a telephone interview this week that watching Mr. Kreh cast reminded him of "Derek Jeter at shortstop — it’s all so fluid, and there’s no wasted motion."Bernard Victor Kreh was born Feb. 26, 1925, in Frederick, Md., the first of four children. His father, Theodore, a bricklayer, died in 1932, and Lefty and his siblings were reared in meager circumstances by his mother, the former Helen Purdy, a homemaker, who later remarried.He learned to hunt and fish as a boy in the woods and streams of central Maryland, but did not discover fly-fishing until after World War II — after he had served in an Army artillery unit in Europe and fought in the Battle of the Bulge.In 1947, back in Maryland, where he had gained some renown as an expert in fishing smallmouth bass, he came to the attention of Joe Brooks, an outdoor writer a generation older than Mr. Kreh."He’d heard about this guy on the Potomac River," Mr. Kreh said in a telephone interview in 2007, "who was catching far more smallmouth than anyone else."Brooks, who would become a famous angler in his own right, asked Mr. Kreh to guide him for smallmouth bass on the Potomac.Watching Brooks cast his fly rod with consummate grace and catch lots of fish with his artificial flies was a transforming experience for Mr. Kreh, who until that day had never seen anyone fly-cast. With Brooks’ help, he bought his first fly rod the next day, and the direction of his career was set.It was also around this time that Mr. Kreh started working as a shift foreman at the federal government’s bioweapons laboratories at Camp Detrick, later renamed Fort Detrick, in Frederick. He liked the job because its irregular hours allowed him to spend a lot of time outdoors.Remaining at Fort Detrick until well into the 1960s, Mr. Kreh later became one of three workers there to be infected with anthrax and the only one to survive. Fort Detrick scientists reportedly collected anthrax from Kreh’s infection and gave it the official substrain name BVK-1.By the early 1950s, Mr. Kreh had been writing a freelance outdoor column for the Frederick News-Post. He went on to write for other newspapers, including the St. Petersburg Times, and the major outdoor magazines before landing in Baltimore as outdoor editor for the Baltimore Sun, where he remained for 18 years before retiring at age 65.Mr. Kreh hardly stopped working, though; he continued his busy career as a writer, photographer, casting instructor, product endorser and A-list angling celebrity.