One of the incredible things about modern digital photography is the sheer processing power. Professional cameras these days can take hundreds of high-quality photos per second and store them all on a card the size of your little fingernail, which means that you never have to miss a second of the action. Shoot first, as the saying goes, and ask questions later.
This results in spectacular imagery like what you're seeing here. A millisecond earlier and this would be a photo of a still patch of water. A millisecond later and the surface of the water would be broken, the magic lost. But in this instant - so easy to capture these days - we find something almost otherworldly, like the swimmer is emerging from an alien sac. Frightening and amazing at the same time.