Somebody in a hotel in Panama City Beach, Florida filmed a shark getting dangerously close to a swimmer in the ocean below. In the beginning you see a dark object beneath the surface of the water. It kind of looks like a manta ray.
After about a minute you can definitely tell it's a shark, and you hear people on the shore yelling at the swimmer to head back. And just when it looks like the shark is going to attack, it turns and goes the other way.
( It comes into view at 0:47, and turns toward the swimmer at 1:43.)