New figures show sewage was released into rivers, lakes and the sea around Wales for more than 800,000 hours last year.
The charity Surfers Against Sewage, which has analysed data from Wales’ water companies, said there were more than 100,000 sewage discharges in 2025 – or one every five minutes.
The figures are down on the year before when sewage was discharged for more than 970,000 hours.
Natural Resources Wales (NRW) said it had strengthened its approach as regulators through increased monitoring and tighter guidance, and had overseen “significant programmes of environmental investment” by water companies.
Surfers Against Sewage said part of the reason for the drop was the dry weather seen during the summer last year, but underinvestment and a lack of enforcement remained an issue.
In its annual assessment, it said since 2019 it had received 992 reports of sickness in Wales caused by sewage, with 215 of those coming in 2025.
It said the impact of those sickness reports led to more than 2,200 days off work.
According to the charity, sewage was discharged into Wales’ designated bathing waters for a total of 35,669 hours over the year.
At Llyn Padarn, Gwynedd, despite the lake’s designated bathing water being classified as “excellent” for water quality, discharges lasted 1,614 hours.
Rules allow a limited discharge of sewage in periods of excess rain, but environmental groups remain concerned the levels pose a threat to wildlife and a health risk to swimmers.