Two beaches fell below minimum hygiene standards for swimmers in the latest study of the country's bathing areas.
Clifden Beach in Galway and White Strand at Miltown Malbay in Co Clare were classed as having poor quality status last year by the Environmental Protection Agency (EPA).
But on the plus side, five local authorities - Dun Laoghaire-Rathdown, Louth, Mayo, Meath and Wicklow County Councils - all earned good marks for high water quality at their beaches and swimming spots.
The EPA said Clifden fell down as it is still awaiting remedial works on the nearby sewage treatment plant, while White Strand suffered due to an uncharacteristically poor sample taken after bad weather.
EPA director-general Laura Burke said Ireland is showing sustained improvement in the numbers of quality bathing areas. "There has been a drop in the numbers of areas achieving 'good' status this year, although five local authorities achieved 'good' status for all of their designated bathing water sites," she said.
"While compliance with current bathing water quality standards is high, stricter standards will take effect from 2014 and these will require greater vigilance to ensure our bathing waters continue to be among the best in Europe."
EPA senior scientific officer Peter Webster urged local authorities to identify more bathing areas for assessment. "Nationally we have approximately 27 beaches per million of the population which is below the EU average and we would strongly encourage other authorities to identify further bathing areas for designation and water quality monitoring," he said.
The EPA report found that 21 bathing spots met only the "sufficient" water quality standard. In Dublin they included Balbriggan front strand, Loughshinny, Rush south beach and Sandymount on the south side of the city.
In Galway they were Traught in Kinvara, Ballyloughane beach, Grattan Road beach, Silverstrand beach and Tra na bhForbacha. In the south of the country the Youghal region fell down on the water quality at its beaches at Claycastle and the Front Strand, while in the north Tra na hUine or Inny Strand at Waterville did not make the top grade.
In the south-east Tramore beach and Duncannon in Waterford and Rosslare and Morriscastle in Wexford were also classed as just meeting the sufficient quality. In the north and north-west Lady's Bay near Buncrana in Donegal and Streedagh beach in Sligo fell below the highest standards.