Athletes who took part in a triathlon event were left “bed-bound” with nausea and diarrhoea after competing in the race’s swimming leg.

Those involved in the event took to social media to question if anyone else had become unwell after taking part in the annual Hever Castle Triathlon last weekend, saying it was “like swimming in a massive puddle of ****.”

The race organisers say water quality tests carried out before the event showed it to be safe, but an investigation has been launched following a number of reports of sickness.

One Reddit user, Whimbler, posted on the discussion site: “Writing on behalf of my partner who did Hever Castle triathlon yesterday, and is now bed-bound with nausea and diarrhoea.

“Was curious if anyone else who raced at Hever yesterday is feeling rough?”

Their post attracted more than 60 replies, with many people saying they too didn’t feel right after taking part.

User 29hungrydingo said: “I did the Olympic on Sunday and have been feeling icky since.

“I got huge stomach cramps on the run and haven’t been right since.

“On Monday I woke up with a total loss of appetite, stomach cramps and feeling below par – Tuesday and Wednesday were the same.

“I feel like I can't pinpoint it to Sunday and swimming in the lake as I haven't had severe symptoms in 36 hours.

“To be honest though, it was like swimming in a massive puddle of ****.

“After the first red buoy turn going to the next green, the water went black - you couldn't see a thing!

“It was like someone turned out the lights. I can't imagine what would be in the water there.”

Others on the thread agreed, claiming themselves or their friends had been ill since the event.

After those affected emailed the race organisers, Castle Race Series, an official statement was released.

A spokesman for the event management company said: “We understand that a number of competitors are experiencing sickness, including diarrhoea and vomiting, having taken part in the swim leg of an event over the weekend.

“We are sorry to hear this and wish you a speedy recovery, if you are not already back to your normal self.

“We wanted to extend a thank you to those who have notified us of their symptoms.

“Understandably, this has left some feeling anxious as to the cause and we wish to reassure anyone about our testing procedures prior to, and during, the event weekend.”

The spokesman explained the Castle Race Series water tests begin six weeks before any race is due to take place and then again four weeks before. Another one is done two weeks prior to the race.

The water samples are taken from the body of water and the tests are conducted in a lab to test for both E. coli and Enterococci to ensure that the water quality is safe to swim in.

In the week leading up to the event, these tests are carried out once every morning five, four and three days prior to the event to ensure the quality of the water has not fluctuated from previous results.

The spokesman continued: “We can confirm that all test results received indicated the water was safe and suitable for swimming.

“We are conscious that harmful pathogens can quickly occur in open water, and, given the heavy rainfall in the week preceding this event, we conducted an additional test as close to the event as possible on Thursday, September 21, to ensure the water was safe. This too came back as safe.

“There is an implied risk when swimming in open water and from the communication received it seems that the most common occurrence causing illness is due to the ingestion of water (whether knowing or unknowing) during the swim.

“Whilst we acknowledge a higher than typical number of athletes notifying us of illness, it appears those affected have recovered within a couple of days from initially becoming unwell.

“The welfare and safety of all our participants and staff are at the heart of our business.

“We are taking this matter seriously and are continuing to investigate alongside the water testing lab and Southern Water to ensure there are no more serious issues at play and to understand if more can be done in future to prevent this.

“If we are made aware of any new information which does not align with this, we will be sure to update athletes where necessary to ensure you are kept up to date.

“Once again we are sorry to hear that some are feeling unwell and wish you a speedy recovery.”

Have you been ill after taking place in the triathlon last weekend? Get in touch by emailing messengernews@thekmgroup.co.uk