Bathing season ends tomorrow, meaning for many designated swimming spots around the Irish coast, no testing on water quality will be done until 1 June 2026.
Local authorities are responsible for the management and monitoring of designated coastal swimming areas, known as bathing sites, and while they can test outside of the bathing season, the tests are costly.
In recognition of 'out of season' swimmers, water testing is now carried out on designated swimming areas in Dublin Bay year-round and is made publicly available via the EPA website Beaches.ie.
The safety of bathing water is governed by the Bathing Water Regulations from 2008. The water is tested for the presence of two bacterial markers, E. coli and intestinal enterococci.
"We're interested in so-called faecal contamination of water, so water contaminated with poo," explained Professor Wim Meijer, microbiologist studying water quality in UCD.
"It these levels in water are high, it means that there is recent contamination and that can bring with it all kinds of disease-causing organisms.
"They may cause a variety of symptoms ranging from very mild discomfort to very severe diarrhoea.
"You can think of skin infections, eye infections, pneumonia, so it's better not to swim in water that that has been that is suspected of being contaminated by faecal matter," Prof Meijer said.
There are three main sources of contamination: sewage overflows, agricultural land runoff and dog droppings on beaches.
Research commissioned by the Department of Housing on the risk to sea swimmers outside of the designated bathing season includes an increased risk of water-borne illnesses.
While most of Ireland’s bathing water quality is deemed to be excellent, the country is below the EU average, and pollution incidences do occur.
"In fairness, most bathing water quality, most bathing waters around Ireland are of excellent quality and there's no reason to assume that suddenly they would deteriorate in October," Prof Meijer said.
"In general, after heavy rainfall we get pollution spikes," he added.
"The best thing is to look at the weather conditions after heavy rain, don't go swimming.
The beach at Ballymoney, Co Wexford has a blue flag, meaning its water quality has been designated as generally "excellent".
However, the water is only tested during the summer months and this summer, the quality has been rated as ‘poor’ three times.
A poor classification means that it is not safe to swim.
'Current system isn't fit for purpose'
Karin Dubsky of Coastwatch regularly swims at her local beach in Ballymoney.
Ballymoney beach has a blue flag, meaning in general its water quality is excellent, but three times in 2025, the water was rated as "poor".
A poor classification means that it is not safe to swim.
"The general gist is that you would have good water quality until you have a burst of rain and then you have a problem," Ms Dubsky said.
"We know there's a caravan park, a sewage treatment plant, some septic tanks, farms, everything, above [the beach], so you only need one of them to overflow," she added.
Although both water quality testing and the lifeguards will stop next week, Ms Dubsky said she and many locals will continue to swim.
Ms Dubsky said if the weather is good over the October midterm break, she would expect even more to swim.
Ms Dubsky said she is not necessarily in favour of more water quality testing as it is costly for the local authorities to undertake and the results of the test can take up to 48 hours, meaning if there is a warning, it may be published too late for swimmers.
"I think the current system isn't fit for purpose," Ms Dubsky said.
"I'd like more attention to proper alerts so that the minute there was an overflow, for example, of a sewage treatment plant, there was an alert.
"I don't think everywhere everybody should be monitored year-round, but I do think before the Christmas and New Year's, you really should have maybe two samples in the week before so people can make a more informed choice [about getting in the water]," she said.
Antóin McDermott regularly swims with his family in Seapoint Beach in Termonfeckin, Co Louth, including outside of the bathing season.
"This beach is actually a really good beach; it's why we come here. It has had excellent water quality and last four years and it's got a Green Coast award," Mr McDermott said.
"But I think what people aren't aware of is that it doesn't mean that the beach is always safe to swim in, it's not always pollution-free.
"If there's been a lot of heavy rain, I would be saying look, let's not go swimming because there's always a chance with heavy rain that you'll get pollution in the water."
In 2024, the water quality at this beach had a rating of "poor" three times. At one of the tests, the E. coli level was three times the limit.
"Because the samples aren't taken throughout the year, if that had happened outside the bathing season, there'd be no signs, and we just wouldn't have been aware of that," Mr McDermott said.
"Bacteria is not very visual. The first sign you might get that there’s been pollution in the water is when you get some sort of gastrointestinal illness," he said.
Monitoring of the water quality is one issue, but as the advocacy manager for the Sustainable Water Network (SWAN), Mr McDermott also wants more to be done to stop the source of pollution.
That requires investment in water treatment facilities and on farms so that heavy rainfall is less likely to lead to an overflow of contaminated water making its way to the coast.
Another issue is that not every coastal area is designated a bathing area and is therefore may not even be tested during the summer months.
Dr Anne Dee, public health consultant and president of the Irish Medical Organisation, explained that bathing water is tested for the presence of E. coli in and intestinal enterococci because they can cause gastrointestinal infection, most commonly leading to diarrhoea and vomiting.
Dr Dee said that although bathing water is tested in a relatively "narrow" period between June and September, that is the period when the water is likely at its safest.
"That's because of the weather conditions associated with summer. Sunlight is actually really good at disinfecting water and also there’s lower rainfall during the summer.
"So, the time when our water is most likely to be safe is during that summer season," she said.
Dr Dee recommends that people use the EPA website Beaches.ie to look up the areas where they plan to swim and the data for the summer will give them an idea of what it will be like in winter.
"If it's good all summer, then it's likely that it's also going to be a low enough risk in the wintertime.
"The bottom line is to you know, try and swallow as little seawater as you can, especially if you're swimming in the winter and to wash your hands when you come out of the water.
Dr Dee added that she recommends swimming as good for both mental and physical health
"Swimming all year round is really good for you," she said.
"It's higher risk in the wintertime, we just need to be a bit more careful," Dr Dee added.
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