The Fins Sharks Like Best

On a baited shark dive during the seasonal sardine run this summer at South Africa's Aliwal Shoal, Paolo Stanchi, a 22-year-old American research diver, became part of the food group. He was bitten by a 10-foot-long dusky shark, and his left leg and both hands were badly mauled. (The boat captain saved his life by stemming the flow of blood, and Stanchi was airlifted to Durban for surgery).

What made the sharks go after Stanchi? Blue Wilderness, the dive operator, believes it was his fins. Stanchi was wearing split fins with grey and black stripes, and Blue Wilderness owner Mark Addison says the shark apparently bit at his fins in a case of mistaken identity, thinking they were really a small shoal of fish.

That's why Jim Abernethy, who runs his Scuba Adventure shark dive trips in the Bahamas, recommends his divers don't wear split fins. "They're easier to swim with but you have to kick more. You have to kick faster to get the same speed as when wearing normal fins. That means more movement, and that attracts sharks. The faster you fin, the more you look like prey, and sharks come in to investigate." And on a shark dive, the last thing you want to do is to attract attention to yourself."

Ralph Collier, head of the Shark Research Committee and author of Shark Attacks of the 20th Century, says the shark might have struck Stanchi's fins because they were closest to it when approaching the bait. "Sharks frequently bite limbs before [they bite] the torso, especially in the case of divers, because they are more readily available to the shark as it nears the subject. Further, I would assume that the vibration patterns emitted by the split fins is different than that produced by a natural prey, the sardines. Therefore, additional motivation could have been the difference between the fin and prey vibrations, and not that they duplicated one another."

Both Collier and Abernethy say the case of 'mistaken identity' is overemphasized. All pelagic sharks have good vision. If they didn't, they wouldn't be such great hunters - - and far more humans would have ended up as shark food by mistake. "In clear water, they'll realize what you are before they get there," says Abernethy. "And they definitely don't want us."