You've just asked one of the fundamental questions in my field, marine ecology. Marine ecologists study how animals and plants interact with their environment. Though it can be hard to tell from our view on the land, the ocean has many different areas for animals and plants to live in. These areas, called habitats have distinct properties such as temperature (a warm area in the tropics or a cold habitat at the north pole), depth (the ocean surface or 30,000 deep), or other organisms present (for example, coral reefs are both living things and habitat for other organisms).

The conditions in each area are very different, and animals often have very specialized and interesting ways to help them survive. For instance, some fish living in the very cold waters at the south pole have antifreeze in their bodies so ice wont form in their bodies and kill them. Animals living at great depth have evolved ways to withstand the crushing pressure. The giant kelp that grows on the coast here at UCSB has air filled floats so that it can keep its fronds up near the water surface, where there is more light for growth. Over and over we find that animals and plants are uniquely adapted to the conditions in which they live. Scientists here at UCSB study a wide variety of marine habitats including coral reefs, deep sea hydrothermal vents, kelp forests, the Antarctic, salt marshes, rocky shores and many more.