CORONADO, San Diego County (CBS / AP) — Authorities say 35 beachgoers have been stung by stingrays in San Diego County.

People wading in the Pacific Ocean encountered the rays throughout the day Thursday in Coronado.

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Lifeguard Capt. Sean Carey tells the San Diego Union-Tribune that more stingrays show up in the warm shallows when the waters are calm.

The flat-bodied fish are shy and tend to hide in the sand but their venomous, barbed tail stingers pack a punch if they’re disturbed. Most stings happen when beachgoers accidentally step on them.

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The stings usually aren’t serious but the pain can last for hours.

Carey says beachgoers can avoid being stung by shuffling their feet when they walk in the water so the rays know they’re coming.

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