Organisers of a charity swim cancelled the event after they found out sewage had been discharged into the sea.
Lyme Splash said 200 people had been due to take part in Sunday’s 3.15km Sea Swim Challenge from Lyme Regis to Charmouth.
But founder and organiser Karen Durham-Diggins said heavy rain had led to sewage discharges.
South West Water, which is responsible for the sewerage network at Lyme Regis, told her it was ‘sorry to hear the swim was cancelled due to weather conditions’. This led some supporters to label the firm’s response as ‘disgusting’.
Last week, several beaches in Devon were also hit with sewage leaks following heavy rainfall which creates storm overflows, overwhelming sewers.
Ms Durham-Diggins, who also organises the town’s annual charity water polo sea championship, said she was ‘angry and upset’ about the pollution.
‘There was already a discharge the previous evening – it was pumping for quite a while – the first people would have been in the water at 9am.
‘I cancelled the swim late afternoon on Saturday once I saw what rain was coming and knew this would happen.’
Because rain and wastewater are carried through the same pipes, overflows act as safety valves during times of heavy rain, preventing sewage backing up into properties.
A South West Water spokesperson said ‘Heavy rainfall across the region at the weekend caused some storm overflows in the area to activate in line with their permits.
‘We are serious about tackling storm overflows and change of this scale takes time, ambition, and increased investment.
‘We are working hard to actively reduce our use of storm overflows across the region as part of record level investment.’
Wessex Water, which manages wastewater in nearby Charmouth, also says it is investing in the network – spending £3m a month on tackling overflows – although its sea overflow at Charmouth has not discharged since May.
Ofwat has proposed that bills should increase by an average of £19 a year between 2025 and 2030.