How thresher sharks use their tails

Thresher sharks... possess the classic shark body plan, but there is one feature that immediately stands out when you look at them - their ludicrously elongated tails. What could such an appendage be used for? Does it help them in propulsion, or do they use their tails as a whip to stun fish before consuming them?

The second method, by contrast, involved the shark swimming up alongside its prey and whipping its tail sideways to strike with the distal end of the tail, and this technique was successful about 92% of the time. What had been presumed for so long turned out to be true - these thresher sharks attempted to shock or immobilize their prey with their tails before consuming it.

More at the link, including still photos; for a video, see the embed at the BBC.