Bay Area: Home to five of California's most polluted beaches

San Mateo County, Calif. (KGO) -- What a bummer! An environmental nonprofit has released its annual list of the 10 most polluted beaches in California based on harmful bacteria levels - and five in the Greater Bay Area made the list.

"You want to have a good time and experience the beach," said San Leandro resident Tiana Webster. "It's not cool if it's polluted and not very clean."

Marina Lagoon at Lakeshore Park in San Mateo came in at number two on Heal the Bay's annual "Beach Bummer List" which was surprising to some.

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"I assume that it's safe, but now this is new, I totally had no idea," said Webster.

The San Mateo County Environmental Health department checks bacteria levels at the beginning of each week, so if the numbers exceed state standards, warning signs go up to alert the public. Poor water circulation and wildlife are typically two of the contributing factors that lead to poor water quality at the lagoon.

"High bacteria counts in the water can lead to a number of health problems including gastrointestinal illnesses, skin rashes, and ear, nose and throat infections," says Karen Vu, Heal The Bay beach water quality analyst.

Linda Mar Beach in Pacifica, as well as Roosevelt Beach and Surfer's Beach in Half Moon Bay were among the top 10.

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Cowell Beach, west of the wharf in Santa Cruz, also made the list for the ninth straight year, but is getting better, according to researchers. The city recent took steps to improve storm drain flows and to reduce bird-related bacteria installing netting under the wharf.

Overall, roughly 88% of the 96 Northern California beaches monitored by Heal the Bay received an A or B grade for this year's report card. Beaches in Southern California also saw an improvement, likely due to less rain last year, which meant less bacteria-laden urban run-off carried out to the sea through storm drains.

"The beaches and stuff are so dirty and you don't want your kids getting sick," said San Mateo resident Ron DiMaggio. "We gotta fix that, hopefully."

Click here to view Heal the Bay's full beach report card for 2017-18.