Dangerously high levels of E coli bacteria have spiked nine times at Dublin Bay beaches since the beginning of the bathing season.
The beaches in question are Dollymount, Merrion Strand, Claremont, Loughshinny and Rush - which is currently underfire as untreated raw sewage continues to flow into the water.
The city's beaches are a hotspot for bathers throughout the year and regularly used in the summer months. But swimmers need to keep a cautious eye on water quality levels.
E coli is measured in cfu - colony forming units - which are indicators of fecal material in drinking and recreational waters and can cause diarrhea and vomiting. Niamh Hatchell of the Environment Protection Agency (EPA) said that water quality is regularly measured in 100ml quantities - if the level of E coli is higher than 500 per 100ml, then the water doesn't pass the quality mark.
The Herald can reveal that E coli levels at Merrion Strand last week soared from 75 per 100ml to a whopping 1,112 per 100ml, with no new readings available.
Last month levels hit the roof with readings up from 31 per 100ml to a staggering 6,488 per 100ml - however, it is not a regular occurrence.
These levels surpassed those found at South Beach, Rush last month. The North Beach at Rush is not an EPA-monitored bathing spot any more. There is a blanket ban prohibiting bathers from entering the water at any of Rush's beaches.
E coli levels at South Beach dramatically increased from 10 per 100ml in May to 624 per 100ml in June. Since then readings have returned to normal at monitored spots - but two other beaches in Rush still have 'do not swim' notices in place.
The situation is so dire in Rush that locals have been spurred to action. Over 100 attended a public meeting earlier this week at Rush Community Centre to discuss the problem of untreated sewage spewing off the coast of their town. Cllr Barry Martin from the Rush Development Committee said that the dumping of raw sewage into the harbour is "an outrage".
"Untreated raw sewage from approximately 2,700 households flows into the sea. The situation in Rush is an environmental emergency. Fingal County Council and all relevant authorities need to treat it that way. Rush is the only town in Dublin facing this issue," Cllr Martin said.
"The youth of Rush can't go to the beach and that's disgraceful, they go down to the beach with the good weather and the beach is closed."
The community have stepped up pressure on Fingal County Council and will hold a meeting next Tuesday, July 21.
A spokeswoman for Fingal County Council noted that following tests on water quality, all monitored beaches in Fingal comply with Bathing Water Quality Regulations.
"The standards for measuring water quality are stricter since 2014 than in previous years," she added.
Despite this swimmers have even been told they face a three-year wait before they can return to the waters in Rush as planned sewage treatment work by Fingal County Council and Irish Water are not scheduled to be completed until late 2018.
"It is not acceptable in a modern economy that so many of our towns are discharging raw sewage directly into the environment and Irish Water is targeting those most in need of investment as our top priority to protecting the environment and allow for growth," said Jerry Grant, Head of Asset Management at Irish Water.
Despite the recent high levels of E coli at our beaches, the EPA says that the quality of Ireland's bathing water in general is excellent, with 94pc of bathing waters meeting the new, stricter, minimum EU standards and achieving at least 'sufficient' water quality status over a four-year assessment period (2011-2014).
Aside from water quality issues, swimmers in Dublin Bay have to be aware of the unpredictable nature of our sea.
The Rnli said that on average there are more people dying in Irish waters than pedestrians and cyclists killed on the roads.
Last year 114 people drowned. The number of near-misses was even higher - there were 1,133 people rescued by RNLI lifeboat crews.