Shark, shadow or other?
That's the question puzzling surfing fans after a clip of Kelly Slater surfing the Box break in Margaret River was uploaded to the Association of Surfing Professionals' YouTube account on April 5.
The footage initially appears to be harmless enough, just one of the countless barrels the world's greatest surfer has caught in the Margaret River region, until the video reaches the 0:17 mark.
A large, long silver shadow flashes through the top of the barrel, leading YouTube commenters and readers of surfermag.com, who posted the video online, to question if Slater had been, to coin a phrase, sharkbombed.
However the debate is far from settled, with commentators saying it could be a surfer pictured in the background at the start of the clip, a manta ray or even the reflection of Slater himself.
While the man himself, who may take on Brazil's Filipe Toledo and French Polynesia's Michel Bourez in heat three of round four of the Margaret River Pro on Wednesday if swell conditions improve by midday, was unavailable for comment, ASP's Steve Robertson said the key to the aquatic mystery lay in unreleased vision from the session.
"There was a actually a pod of dolphins in the area at the time, and Kelly actually got off the board and has essentially taken an underwater selfie with these dolphins," he said.
"There's no doubt about it, it's not a shark, it's not a ray or another surfer, it's actually a dolphin in the footage.