Did you know that naturally occurring oil seeps from the seafloor are the largest source of oil entering the world ocean? In fact, they account for nearly half of the oil released into the ocean environment every year. Seeps occur when crude oil leaks from fractures in the seafloor or rises up through seafloor sediments, in much the same way that a freshwater spring brings water to the surface. The waters off of Southern California are home to hundreds of naturally occurring oil and natural gas seeps.