Odds are the world of capital-F fashion never gave a moment’s thought to Jimmy Buffett, the bard of Margaritaville, who died on Friday at 76. Yet the truth is the undisputed king of easy-listening yacht rock probably exerted as much influence on style as any designer that ever sent a model down a runway in a jacket with three sleeves.

It is not just a matter of the crazily festooned novelty hats his fans — known as Parrot Heads — sported at his shows. Mr. Buffett, a singer, songwriter, entrepreneur and best-selling author, took a form of laid-back dressing instantly recognizable to anyone who ever hung around a boatyard and made it mainstream both at home and abroad. Not for Mr. Buffett the hippie-adjacent suedes and leathers of his musical contemporaries, nor even the standard-issue double-denim get-ups preferred by pop folk idols of his age, people like James Taylor or Jackson Browne.

A lifelong waterman, Mr. Buffett spent his early days propping up bars in Key West. Like many before him, he was quick to adopt the locals’ casual garb. Nobody wears uniforms on Key West, unless you think of a uniform as Bermuda shorts in Easter egg colors; low-slung, faded khakis; flip-flops; and short-sleeved shirts with raucous patterns and squared-off tails.

The raggedy straw hats or duck-billed oysterman caps of the sort Papa Hemingway once wore on Florida’s bonefishing flats were all Buffett staples, part of an image cannily cultivated by an entertainer who, while evangelizing for leisure, built a personal fortune on themed restaurants, casinos, hotels and cruises. Though the company is privately held, by most accounts his branding savvy made him a billionaire.

So readily identifiable are the elements of that brand that the internet is awash in suggestions on how to strike the right “festival attitude’’ for a Jimmy Buffett concert or Jimmy Buffett party and instructions for groomsmen and bridesmaids on what to wear for a Jimmy Buffett-themed wedding. Apparel companies like Marine Layer, founded just over a decade ago in California by Michael Natenshon, started out with the clear intention of making clothes so casual they looked as if they were fished from the back of the closet. If you riffle through the stock at any of Marine Layer’s 40 stores, you inevitably feel you have wandered into Jimmy Buffett’s life.

There are faded shorts in pinwale corduroy with six-inch inseams a lot like those produced by Jim Jenks when he founded his wildly influential surfwear brand Ocean Pacific (Buffet wore them onstage) in 1972. That, of course, was around the time Mr. Buffett was recording his second album, “A White Sport Coat and a Pink Crustacean.’’ Posed on a fishing boat for the cover, Mr. Buffett wore bell-bottom denims and a broad-brimmed Stetson. By the time raunchy tunes like “Grapefruit-Juicy Fruit’’ and “Why Don’t We Get Drunk’’ became barfly anthems, Mr. Buffett had already shed the hat (and, eventually, the hair beneath it), trading his slick denims for outfits so aggressively understated it seemed as if the big wardrobe choice of his day was whether to go commando.

“He didn’t identify with fashion statements per se,’’ said Kevin McLaughlin, a co-founder of the prepwear mini-empire J. McLaughlin and driving force behind the re-envisioned heritage label Quaker Marine Supply. “But he set a standard and had an influence in that if you’re cool and you’re comfortable in your own skin, it’s almost impossible to be underdressed.’’

Case in point: Mr. Buffett’s decision to pick up an honorary doctorate in music from the University of Miami in 2015 wearing flip-flops and sunnies with his cap and gown. “Our industry rewards elegance and style,’’ said Mr. McLaughlin. “Jimmy took the reverse approach, based on a level of self-confidence.’’

Call it nonchalance, sprezzatura or swagger — that offhand assurance is a quality too little appreciated by contemporary fashion, where the benchmark of critical success is often looking overdressed, overthought, overwrought. Mr. Buffett, who divided his time among residences in Sag Harbor, Palm Beach and the Caribbean island of St. Barths, moved in sophisticated, worldly circles and was a far cry from the parody of a yacht bum.

Yet he retained the cool he developed as one in a coterie of writers of the raucous, drug-addled Key West literary scene of the 1970s.

In a documentary short about that time, “All That Is Sacred,’’ that premiered at this year’s Telluride Film Festival, the writer Thomas McGuane, who is married to Mr. Buffett’s sister Laurie, said he had suggested to his brother-in-law that he write a song about those days called “Last Man Standing-ville.” “That’s too close for comfort,’’ Mr. Buffett replied, prophetically as it turned out.