Introduction | How Does Water Get In and Out of Oceans?
Who Needs Oceans? | When Saltwater Meets Freshwater!

Some people like to visit beaches that are at the edge of oceans, sail on top of oceans, or swim within them. Even if you live a thousand miles from an ocean, or have never seen one, oceans affect you and the weather where you live. The rain and the snow that fall in your town were probably water in an ocean just a few days before.

The salty water of the oceans covers almost three-quarters of the Earth’s surface. There are four different oceans on Earth: the Pacific, Indian, Atlantic, and Arctic Oceans. All the oceans are connected to each other. Water is always moving within and between the oceans in currents, tides, and waves.

The oceans are so old that, over time, minerals have dissolved into the water that make it taste salty. Much of the salt in the oceans is made of the same stuff as ordinary table salt. When water evaporates from the surface of the ocean, the salt stays behind.