Jimmy Buffett Didn't Slow Down as He Faced Cancer — or Sharks! — Says Friend Carl Hiaasen (Exclusive)

The author exclusively tells PEOPLE that his longtime friend Buffett was “larger than life” and “invincible"

Jimmy Buffett's longtime friend Carl Hiaasen is paying tribute to the late singer-songwriter's strength and love of life.

Celebrating the resilience of Buffett — who died on Friday at the age of 76 after a diagnosis of Merkel cell carcinoma four years ago — Hiaasen exclusively tells PEOPLE that doctor's orders didn't slow the "Margaritaville" singer down. And neither did any potentially dangerous sea creatures, for that matter.

“I was with Jimmy in the Bahamas in October of 2022,” the author, 70, says. “He was supposed to take it easy although he didn’t know what that meant. He was fishing when a large lemon shark was heading for him. He had a drone up because he wanted a video of this experience. He was so excited because he wanted to put it on stage while he was performing during his next tour when he performed his song 'Fins.'”

“The shark was really close but Jimmy was so excited," Hiaasen added. "He was planning for where this video would go in his show. There was no way to slow him down!”

Related: Jimmy Buffett's Cause of Death Revealed as Merkel Cell Skin Cancer

Hiaasen, who calls Buffett “larger than life” and “invincible," even mentions the singer-songwriter in his upcoming children's book Wrecker, which is set in Key West, Florida. He was able to show his friend the book, which is set to be released on Sept. 26, before he died.

On the same trip that the duo had the shark encounter, Buffett also worked his way around a foil surfboard.

“He just got up and disappeared even though he was told to take it easy. We couldn’t see him and were trying because we wanted to know where he went," Hiaasen recalls. "After five or more minutes, he came back, hopped off, and was as happy as can be.”

“I truly thought he could beat this because he had such a phenomenal attitude,” Hiaasen added. “This is so hard for me to accept or talk about.”

Related: Jimmy Buffett, 'Margaritaville' Singer, Dead at 76

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Shortly after Buffett's death was announced on social media over the weekend, an obituary on his website revealed that he died following the diagnosis of the rare, aggressive skin cancer. The singer-songwriter continued to perform through treatments, the obituary noted.

Celebrity friends and fans have continued to remember Buffett with moving tributes throughout the weekend, with the likes of Andy Cohen, Miles Teller and President Joe Biden paying their respects.

On his own Instagram page, Hiaasen shared an image of himself and his friend in the cockpit of a what appeared to be a plane, calling Buffett's death "heart-crushing news."

"Nobody had more pure fun in life, or worked harder to share it with others," the Hoot author wrote on Saturday.

"He lived true to his songs, and he was writing with joy until the end, tweaking the final cuts on a new album. Jimmy had one gear: moving at the speed of light, even in flip-flops. He was, literally and exuberantly, all over the map. Richly talented, wonderfully generous, and wildly passionate about the places he cherished – peaceful islands and harbors where he transported everyone who loved his music."

Hiaasen added that Buffet was "happiest on stage, whether it was a bar in Key West or center field at Fenway Park."

"I’d like to think that somewhere is a pristine stretch of Caribbean beach where we still might find – propped against a palm tree — a fly rod and a Martin guitar," he wrote. "And, riding the waves, a familiar bionic pirate on a long board, grinning about all the cool s--- he got away with. I’ll miss you, JB. Millions will. Thanks for the laughs, the adventures, and the unforgettable sound track."

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