CHATHAM (CBS) – Just when you think you’ve seen it all…you haven’t seen this.

The YouTube video, which initially showed up on Barstool Sports, shows a man was fishing with his friend off the coast of Chatham recently when they encountered a large basking shark. The person who posted the video estimates the shark to be 20+ feet long.

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As the shark swam under their boat, one of the men stepped to the edge of the boat. The man then dove into the water headfirst. It appeared as if he was attempting to ride the shark or possibly swim with it.

Watch video:

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The man could be seen swimming back to his boat, yelling “Woo!”

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Basking sharks typically live off New England year-round and can be up to 40 feet long, according to the New England Aquarium [.pdf]. They are largely harmless to humans.