Supercavitating, rocket-powered torpedo (red) travelling through the sea in a bubble of its own creation. The flattened nose creates areas of very low pressure that result in bubbles (cavities). When these merge into a bubble that encloses the projectile, it is called supercavitation. Gas is expelled at the nose to help with the bubble creation. The cavity (containing water vapour) dramatically reduces the drag on the torpedo, so that it flies like a missile, many times faster than a conventional torpedo.