A blowhole is the nostril on top of a whale's or dolphin's head that they use for breathing. Unlike humans, who breathe through their nose and mouth on their face, whales and dolphins have their breathing hole on the very top of their head. This clever placement lets them breathe while most of their body stays underwater: they just need to break the surface for a moment, take a breath, and dive back down.

When a whale exhales through its blowhole, you often see a tall spout of mist shooting into the air. This happens because the warm, moist air from the whale's lungs hits the cold ocean air and creates a visible cloud, just like seeing your breath on a winter day. Different whale species produce different shaped spouts: a humpback whale's spout looks like a bushy cloud, while a blue whale's spout can shoot nearly 30 feet straight up.

The word also refers to a hole in coastal rocks where waves force water and air upward in a dramatic spray. When ocean waves crash into underwater caves along rocky cliffs, the pressure can send water shooting up through cracks in the rock above, creating a natural fountain. These geological blowholes can be dangerous to visit because waves are unpredictable and the rocks can get slippery.