Up to 40,000 people are affected by the contamination and supermarkets are quickly selling out of bottled water.

Residents in some NSW Central Coast suburbs have been advised to boil their tap water due to the possible contamination of the local water supply with E. coli bacteria. A "boil water alert" was issued by Central Coast Council last night after recent samples detected the presence of E. coli bacteria.

People on the Central Coast have been instructed to boil tap water before consuming it after testing detected E. coli bacteria in the local water supply.

Almost 50,000 residents on the Central Coast have been told not to consume tap water unless it has been boiled, after sampling revealed the water supply had " potentially been compromised".

A man has died after he was pulled unconscious from the water at a NSW beach. The man, believed to be aged in his 70s, was pulled from the water at Terrigal Beach on the Central Coast about 8.20am on Wednesday.