. >> reporter: mara diaz is a water quality manager for surfrider foundation, a nonprofit founded byurfers in california nearly 40 years ago. since then, it's transformed into an army of volunteers with 60 labs across the country. >> we're trying to fill in the gaps of the agency-run beach programs. so our volunteers are testing where the agencies aren't. and there is still work to be done. >> reporter: mara coordinates the testing, include hearing on long island, new york. >> we're testing for fecal indicator bacteria. when there is fecal pollution, there are pathogens and things that could cause you to be sick. for instance, i see there are some bird droppings. that's one of the sources of pollution. >> reporter: next up the team heads back to the lab to incubate the samples. >> we're going to go ahead and read our early samples. i'm going put it under the black light and see it glow and then go ahead and count the cells. have i 37 large wells, and have i five small wells. >> reporter: just like one-third of tests they run here, red flags. >> a high bacteria reading? >> yes, for th