An Australian man who thought it would be a good idea to climb on top of a floating whale carcass now regrets his decision.

Amateur whale rider Harrison Williams was filmed mounting the dead animal while sharks fed on it.

"[I was] out on the boat with the boys and one of my mates thought it'd be pretty funny if I surfed the whale, so I just did it," Williams told Australia's Seven Network.

His friends apparently didn't see that there was at least one great white shark in the water. Fortunately, the sharks were too preoccupied with their meal to care about Williams.

Williams, who is from Perth, Western Australia, told Seven that he wasn't too concerned even after he saw the sharks. His friend piloted a boat over to him and rescued him from the carrion barge.

He regrets his decision now, and said his parents are pretty mad with him.

"Mum thinks I'm an idiot, Dad's not too proud either," Williams said. "[I'm] pretty grateful to still be alive."