Outdoor swimmers and triathletes have been told they are not allowed to swim in a Rickmansworth lake because of dangerous swans, algae, and the risk of drowning.

The sport of "wild swimming" takes place outdoors in lakes and rivers, such as those found all over the Three Rivers area.

However, the district council has banned anyone from swimming in the Aquadrome, because it believes it is unsafe.

Molly Fletcher from the Outdoor Swimming Society learned to swim in the lake when she was a child.

She said: "People used to swim in the lake all the time and it was a wonderful family activity. In the 1970s a sailor drowned and after that 'no swimming' signs went up and that was the end of that.

"I looked on Google and there are 25 lakes in the River Colne valley. Four of them are for sailing, there are fishing lakes, birdwatching spots, but nothing for outdoor swimmers.

"Three Rivers District Council just keeps saying no to allowing swimming or triathlons."

As part of an ongoing campaign, swimmers wrote in to the Watford Observer, and 700 people signed a petition to be able to swim in the lake.

Steven Halls, chief executive of Three Rivers District Council, said: "The health and safety of our residents must come first and it is for these reasons that we will not permit swimming in Bury Lake.

"Not only are there serious health concerns about the water, such as the presence of bluegreen algae, but there have been tragic cases of drowning in the past."

However, Ms Fletcher argued: "The council gave seven reasons initially, including dangerous swans. The sailors could equally get attacked by swans if they capsize.

"Swimmers stay much closer to the shore compared to sailors who go right out into the middle and are fully clothed.

"I was also told there is bluegreen algae and Weil's disease in the water, but it's a lovely lake, the water quality is excellent.

"All of the reasons are equally applicable to sailors."

As well as outdoor swimmers, two triathlon clubs in Rickmansworth and Watford have expressed an interest in being able to swim in the lake.

Ms Fletcher said: "Triathletes have to swim in cold outdoor water for their sport and they have nowhere to practice. One of the triathlon clubs in the area has to go the Serpentine in London.

"Swimming outdoors is completely different to swimming in a pool, it's like saying instead of going rambling in the countryside, go to the gym and use a treadmill.

"It's invigorating swimming in cold water, it makes you feel alive and closer to nature, to see the birds and the sun reflecting off the water is brilliant."

Mr Halls added: "Only if the Outdoor Swimming Society can strictly control and manage swimming on the lake, including providing and paying for the appropriate signage, safety measures, public liability insurance and cover of lifeguarding facilities all year round - and this council can be satisfied that all the necessary safety precautions are put in place and be indemnified against any incidents that may occur - will the council reconsider its position."