"I find it very difficult to draw a line between what's sex and what isn't," says Icelandic singer Bjork. "It can be very, very sexy to drive a car, and completely unsexy to flirt with someone at a bar." You could spend all day plugging away in front of Red Tube, for instance, and you still wouldn't see anything quite as sexual as this. It's plain naughty, it's pure filth, in fact it's downright rude - it's Kelly Slater in slow-motion and 4k resolution, bashing out a gouge of near-orgasmic precision. Footage by Aaron Lieber.