Hunstanton is the latest beach to be affected, with the Environment Agency (EA) advising against bathing due to a short-term pollution risk.
The warning follows similar alerts at Heacham, where an incident was reported last Thursday is still in force.
The EA’s website said: “This bathing water is subject to short term pollution procedures.
“The Environment Agency makes a daily pollution risk forecast at this site based on the effects of rain, tide, wind and seasonality on bathing water quality.
The water off Heacham has been rated poor and people warned no to swim again (Image: Chris Bishop)
“After a short term pollution event, levels of bacteria typically return to normal after a day or so but it’s possible to have several warning days in a row.”
Heavy rain on the coast has been identified as a contributing factor, washing bacteria from wild animals, livestock and urban drainage into the sea.
The water at Hunstanton’s beaches is usually rated “good” by the EA, while Heacham’s were rated “adequate” last November after years of poor water quality blamed on sea birds.