Why do whales jump out of the water?
"There are two basic ways for a whale to jump out of the water, or breach. The first kind of breach is the 'Whoops, I was chasing something so fast that I fell out of the water' type. Most kinds of whales breach in this way. They usually hit the surface at a shallow angle and pop only partway out of the water.
"The second kind is the 'I'm going to launch' breach, which takes the whale much farther out of the water. Only a few species do this type, mainly right whales, sperm whales, and humpbacks.
"No one knows why whales do this second kind of breach. Some scientists think breaching might wash parasites off the whale's skin. Another idea is that breaching might be a way to stun or scare fish, making them easier to catch. Finally, a whale might breach to communicate some message to another whale.
"The last of those ideas is based on the fact that whales seem to breach more when they are in or near groups. The breaches might mean 'Hey, look!' or 'Back off!' Or they might not mean much of anything. In other words, the whales might just be playing."
Sarah Markosky, Age 8 Pennsylvania