We turn to a wild video gone viral. See this florida teen hitching a ride on the back of a 30-foot whale shark. Risky stunt is sparking controversy. Abc's matt gutman has the story. Ready? Reporter:... See More
We turn to a wild video gone viral. See this florida teen hitching a ride on the back of a 30-foot whale shark. Risky stunt is sparking controversy. Abc's matt gutman has the story. Ready? Reporter: To chris grace it looked like the world's biggest going by board. I decided, you know what, should maybe go swim with him because I might not be able to do it ever again. Reporter: A whale shark, the world's biggest fish as big as a school bus was cruising off the gulf coast of florida when 19-year-old and his family spotted it. Almost like an adrenaline rush. Reporter: Whale sharks are continued the gentle giants of the sea but he knew it was time to let go. He began to descend and if something doesn't want you on it he might as well let it go. Reporter: It lasted nine seconds. Awesome. Reporter: Followed by the scramble back to his skiff and later a boatload of scrutiny. When people spend a lot of time and a lot of pressure on a fish, it takes away that slime covering and potentially has negative health impacts for the fish. Reporter: These types of interaction between man and sea creature have increased lately raising questions about how much they should be able to encroach. William waterman was arrested last february after police spotted the photos he posted on facebook. Hugging, touching or harassing protected manatees is illegal in florida but this florida woman didn't get the memo turning herself in for the same crime last year after she was photographed hitching a ride on one of these docile creatures. As for grace, he said he'd do it again with some minor changes. I would not necessarily maybe hold on to it, I would absolutely swim with another whale shark. Reporter: For "good morning america," matt gutman, abc news, miami.
This transcript has been automatically generated and may not be 100% accurate.