Dolphins that appear to be closely bonded may swim in synchrony, twisting, turning and swimming in perfect harmony together. Their teeth are interlocking rows of conical pegs, suitable for holding slippery fish. They eat their fish whole, head first. In the wild an open mouth is a sign of aggression, as is head nodding. A sign of greater aggression is violent jaw clapping.
Dolphins breathe through their blowhole located at the top of their head.
A dolphin may empty and refill its lungs in less than a fifth of a second. As the dolphin breathes the air leaves the blowhole at speeds of over 100mph. Complex nerve endings around the blowhole sense pressure changes so the dolphin knows exactly when the blowhole is in or nearing the air and can be opened. Water in a dolphin's blowhole will actually drown it so powerful muscles close the blowhole as it dives under the water again. The dolphin's eyes produce a special slippery secretion which protects the eyes from foreign objects and water friction.