The archer fish catch prey with a water pistol technique. It makes the equivalent of a gun barrel by pressing its tongue against a groove in its mouth, closing its gills to force out the water in a jet. It is accurate up to two metres. This expert in ballistics even allows for the curving of the jet of water through gravity. It also adjusts for the way light bends between the boundary between water and air, which appears to shift the position of the target. By some amazing computation it changes its firing angle to compensate for this optical illusion.