Five out of seven beaches singled out for being sub-standard are in Dublin.
The Environmental Protection Agency has labelled the water quality 'poor' Merrion Strand, Loughshinny, Portrane and Rush South; while Sandymount Stand is new to the list.
Senior Scientific Officer Peter Webster says its harder for urban beaches to meet standards
"They come under a great deal of pressure form multiple sources such as streams, people walking dogs, sea birds and even from the sand itself."
He's also revealed that in some parts of the capital, 1 in 12 houses are connected to storm drains rather than sewers.