|MadSci Network: Earth Sciences|
Many kinds of bacteria can live in the ocean.
The three that are typically tested for (with respect to pollution) are E coli (total coliform), fecal coliform, and enterococcus. They're tested by the county, the testing is state- mandated (AB 411) with specific requirements for what closes a beach. p>
The bacteria themselves aren't necessarily what we're worried about, but they are used as indicators for other nasty things that could make us sick. There are certainly other bacteria in the water, but nobody's looking for them. There has been some talk of developing tests to look for viruses (e.g. Hepatitis A).
The National Resources Defense Counsel (NRDC) did a study (which helped prompt the passage of AB 411) showing that swimming near a storm drain with high "most probable number" (MPN) of those three bacteria made it more likely for the swimmers to get sick.
Some good sites to search for things like this are:
Santa Barbara Surfing
I hope this helps.