The coastal waters are the part of the ocean with which we're most familiar. They’re also the part where the majority of marine life lives. It’s comfortable in these areas. The shallower waters usually mean plenty of sunlight, more moderate temperatures and lots of food. But what about the rest of the ocean – that vast blue universe which lies beyond the boundary of the coastal waters? This is the open sea, and it ranks as the most mysterious, unexplored realms on Earth. The open sea is so big in fact – covering nearly 70% of the planet’s surface – that it’s nearly impossible to imagine it all so scientists have broken the ocean up into distinct areas called “zones.” Understanding these zones will help you understand the complexity of the ocean. To begin exploring, click on one of the ecosystems listed below.