An individual dolphin can take advantage of its speed and rostrum, which is its long, bony snout, to deal a lethal blow to a threatening shark. The dolphin swims underneath the shark and attacks it from below, ramming the soft underbelly of the marauding predator.
The blow usually stuns the shark, but it can be strong enough to render it unconscious or even kill it. If two or more dolphins are present, the shark, despite its thick carapace of sandpaper-like scales and incisor-like teeth, doesn't stand a chance. If it can, it usually swims away. Quickly.