In short, pant-soilingly scary.
Last year, a team of scientists from Woods Hole Oceanographic Institution created the REMUS 'SharkCam' underwater vehicle which they intended to drop in the ocean off Guadalupe Island in Mexico to film great white sharks in the wild. Little did they know how successful they'd be.
The 7-foot long submersible was rigged up with six cameras and a microphone to capture great whites in their natural habitat, and had special equipment to tail the beasts. And then the tables turned.
We're never getting in the sea again.