Residents of the Co Galway village of Roundstone say an outbreak of cryptosporidium will affect this summer's tourist season.
Over 300 residents of Roundstone, Inishnee and Errisbeg have been told to boil tap water before drinking it or using it for food preparation.
The advice follows yesterday's confirmation that the water supply is contaminated with the cryptosporidium parasite.
The area attracts more than 7,000 visitors during the peak tourist season.