LOS ANGELES — Ricky Grigg, a former top-ranked big-wave surfer and oceanographer whose work confirmed one of Charles Darwin’s theories about the origin of tropical islands, has died. He was 77.

His wife, Maria, said Saturday that Grigg died of pneumonia May 21 at his home in Honolulu.

The celebrated surfing pioneer was also a marine researcher who explored undersea volcanoes and once spent 15 days submerged off the California coast in an experimental capsule called Sealab II, the Los Angeles Times reported Saturday.

Richard Wayman Grigg was born in Los Angeles and grew up in Santa Monica. As a youth, he traveled the California coast in search of big waves.

In the 1960s, Grigg was the world’s top-ranked big-wave surfer. He appeared in more than a dozen surf movies and did a turn as a surfing coach for a 1964 episode of the TV drama “Dr. Kildare.”

As a surfer, Grigg was known for exuberantly raising his arms over his head at points during his ride.

Grigg had “a classic style,” Fred Hemmings, a former world champion surfer who went on to become a Hawaii state legislator, told the newspaper. “He stood erect, and his lines were long and clean. I was a half-generation behind him, and he was one of my heroes.”

As an oceanographer, much of his research centered on the atolls and submerged islands of the Hawaiian-Emperor chain, an archipelago extending nearly 4,000 nautical miles into the Pacific. At its northwest reaches, he discovered the “Darwin Point” – a latitude at which, for various reasons, the growth of coral colonies slows and the volcanic islands built upon them start to “drown,” the Los Angeles Times reported.

To measure the growth of coral in a vast ocean realm and get a sense of islands rising and sinking, Grigg organized dozens of researchers in airplanes, boats and submersibles.

Their study, which took five years, was the first to probe the remote reefs, a collaborator, University of Hawaii oceanographer Steve Dollar, told the newspaper.

Grigg also explored volcanic activity beneath the waters off Hawaii. In 1971, he and Dollar dived into a sea steaming with molten lava from a volcano. Dodging a layer of scalding water and streams of cascading lava, they came upon a twisting, ropy tangle of exploding volcanic debris.

“We decided to collect a couple of samples, take a dozen or so quick pictures and then get the hell out of there,” Grigg wrote in his 2012 book, “In the Beginning: Archipelago, The Origin and Discovery of the Hawaiian Islands.” They were the first divers in history to witness such a spectacle, he said.

Data gathered by Grigg and his colleagues helped establish in 2006 the Papahanaumokuakea Marine National Monument, a stretch of ocean and tiny atolls whose total area is larger than that of all the U.S. national parks combined.

He was diagnosed with throat cancer in 2003, the Times said.