The Mere Mile is being held on August 30, Bank Holiday Monday, at Ellesmere.
Swimmers will undertake a mile or 2.5 mile challenge in the town's mere for the benefit of The Robert Jones and Agnes Hunt Orthopaedic Hospital.
It is being held by the League of Friends to the hospital and hosted by Swimfininity, which holds swim sessions and lessons at the mere.
Described as a fun and friendly charity swim it is aimed at swimmers of all age and ability.
James Bainbridge from Swimfinity said: "The registration fees are low with a goodie bag, a bunch of local business offers, event hat and finishers momento along with with the satisfaction that comes from supporting a local charity."
Those taking part range from swimmers who will be attempting their first mile in open water to experienced athletes.
Dr Ruth Longfellow chief medical officer at the orthopaedic hospital said: “I have chosen to take part as I want to support our league of friends, which has been so supportive of RJAH staff over the last 18 months during the pandemic."
She said she was a keen open water swimmer and had enjoyed an open water technique session with Swimfinity, improving my stroke and sighting, to make sure she swam in a straight line .
Places are limited and those wanting to take part are being urged encouraged to register sooner rather than later.
To secure a place to undertake the mile or 2.5 mile swim please email firstname.lastname@example.org or call 01691 404401.