A surfer named Doug Niblack had an insane shark encounter that he was lucky to walk away from unharmed. While surfing, something jarred his surfboard. When he regained his footing, he found himself standing on a shark's back.
He scrambled back to his board and paddled back to shore. Thankfully, the shark had lost interest in him.
The shark was likely investigating the surfboard, thinking it might be a seal. Wasn't a seal, just a very surprised surfer.