I used to think that Jaws was the scariest threat that may be lurking — unseen — under the waves.

But I've realized that while shark attacks may grab the spotlight, most of us never worry that we could taking a dip in surf that's contaminated with sewage, medical waste or something equally horrifying.

Ocean pollution — especially at popular beaches — may be the real threat during a day at the beach.

The Environmental Protection Agency just issued its annual report on beach conditions. The upshot is that while the majority of beaches were open last year, there were some closings due to run-off pollution, unsafe levels of contaminants, microbes, and otherwise nasty conditions.

Fortunately, the National Resources Defense Council offers updated, local-ish information on specific beaches at their excellent and very comprehensive Oceans site. It's also a good resource for anglers, snorkelers, divers, boaters, and pretty much anyone heading for a coast.

They've also posted general tips on their site on what to look for in order to avoid taking a dip in a polluted beaches. Here's a quick rundown:

• Opt for beaches near open water or far from urban areas. Remote locations generally pose less of a health risk than crowded beaches, enclosed bays, or harbors with limited water circulation.

• Steer clear of pipes along the beach that drain stormwater runoff from the streets. They are likely to be more contaminated, so it's best not to swim near them.

• Avoid swimming in beachwater that is cloudy or smells bad.
  
• Keep your head out of the water.
  
• Heavy rains can pollute beach water, so don't swim immediately after heavy rains. Wait about 24 hours.

• Do the right thing, and alert local health officials if you suspect beachwater contamination. That good deed may protect others from hazards or unnecessary exposure.