A Bayport man who said he witnessed a seaplane crash in Great South Bay Tuesday morning said he was "shocked" that the pilot attempted to take off, considering the conditions.

"It was windy out and it was choppy, and I think maybe he got a foot off the water and boom! All of a sudden, it just went in, nose-first," Peter Williams said, adding: "He caught a wave, I guess. Maybe. He went right down . . . fast."

Williams, who lives at the end of Gerritsen Avenue, right on the bay, said he immediately jumped into his 25-foot Grady White, headed to the scene of the crash -- calling 911 en route to report the crash.

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He found the pilot, identified by Suffolk County police as Joseph Cannizzaro, 57, of Bayport, standing on the pontoon of the partly submerged single-engine, amateur-built experimental Kitfox II seaplane.

Cannizzaro was uninjured in the crash, officials said.

Arriving at the scene, Williams said he asked the pilot: " 'You all right?' He said, 'I'm OK.' I threw a line to him."

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Suffolk County police and the Federal Aviation Administration said the accident occurred around 6:45 a.m. about 1,000 feet off the end of Gerritsen Avenue.

The cause of the accident is under investigation.

Emergency responders investigate a call of a plane making an apparent forced landing Tuesday, Sept. 8, 2015, in the Great South Bay about 1,000 feet offshore at the end of Gerritsen Avenue in Bayport, Suffolk County police said. Police said first responders found the pilot, wearing a life jacket, on a pontoon. Photo Credit: James Carbone

Photos from the scene showed the plane sustained significant damage in the crash.

The pontoons were turned upside down. The wing was damaged, the left wingtip split apart from the impact.

Police said Cannizzaro was alone in the plane. A spokesman for Community Ambulance Company of Sayville said the pilot refused medical attention at the scene.

Williams said that, from his vantage point, it appeared the plane hooked a wave with its pontoon while trying to take off. Wind and wave conditions at the time were not immediately available Tuesday.

Police also said the plane's pontoon and left wing "caught water," causing it to crash.

"The seaplane had achieved very little altitude," police said in a statement Tuesday.

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Williams said he struggled to tow the plane to shore and was assisted later by a Suffolk police Marine Bureau crew.

He said the Islip Town constable, as well as crews from the Bayport and Sayville fire departments, also responded to the scene.

Williams said that after throwing the pilot a tow rope, he gave the man instructions on how to tie it to the partly submerged plane -- and the pilot said he wanted to tie it up a different way. "I told him, 'Your idea's what got you into this [expletive] mess."

Police said the seaplane was released to Cannizzaro later.