The oceans' physical properties affect what organisms can live there. For example, sunlight can only penetrate to certain depths of the ocean, limiting where algae and phytoplankton can survive. Organisms typically have tolerances for salinity and temperature; conditions that are too hot, too cold, or too salty limit the species that can survive in specific ocean habitats.

The ocean can be divided into zones according to depth, and it can be characterized by the amount of sunlight that can penetrate through the water column, the temperature and salinity profiles, as well as the types of habitats & ecosystems that exist there. Organisms in the oceans have adapted unique lifestyles for surviving and thriving in extreme physical conditions. The videos and interactive lessons on the following pages will allow you to explore the different light zones, habitat zones, and lifestyles of ocean life.