Worthing Kids and Dapper Snapper runs theraputic swimming classes for its members, among other activities.
The classes were funded until recently by a business, but it is no longer able to subsidise them.
Activities co-ordinator Lydia Wilson is appealing for a long-term sponsor, or group of sponsors, to now come forward to help.
She said: “While we will teach the children how to swim if they can’t already, the sessions are useful for muscle tone, co-ordination and confidence, as well as teaching them how to swim safely.
“We run a total of six classes and there isn’t another similar activity in Worthing as far as I know, so the swimming school fills an important need.”
Running the swim school can cost up to £800 per month, inclusive of pool hire, swimming instructor and lifeguard fees, insurance and replacing equipment.
The group recently received a number of short-term donations, but is hoping to secure future funding to ensure a variety of activities can be run.
Mrs Wilson said: “We received a donation of £500 from Worthing County Local Committee, and Julian Church and Associates kindly donated £300 this month.
“Both of these donations were very welcome, and took the pressure off in the short-term.
“But we urgently need a long-term sponsor, or group of sponsors, and any contributions would be very gratefully received.”
The charity runs a number of other events throughout the year, which are part-funded by parents and fundraising events.
But swimming is the most expensive activity, and a fifth of its 200-strong membership regularly attend the sessions.
Mrs Wilson said: “We could run the schools for a while on money from our resources, but the general pot is used for a large variety of events.”
One such event was a pirate-themed party at Worthing Assembly Hall on Saturday, in celebration of the charity’s seventh anniversary.
Mrs Willson said: “It was an amazing party, with entertainment from Dave Hunt, a lottery-funded pirate play session, polka dot photography and lots of fabulous cakes, which were donated.
“It was a great success and the children looked like they were all having a wonderful time.
“It was a fantastic way to celebrate seven years.”
Those interested in sponsoring the charity should call Mrs Wilson on 07570 768893.
To find out more about WKDS, visit www.wkds.org/wkds