Dalyan, Turkey
You can take one of the water bus services that goes down river in about 20/30 minutes to the Beach. On the sandy beach there are plenty of sun beds, changing facilities, first aid, wc and cafe. We also hired a private boat for our group of 12 people, which takes you along the River and Coast for some swimming and a really delicious BBQ. If you are going, I would recommend trying to secure Poseidon 48, which is run by a mother and son, who were lovely. We enjoyed our trip so much we re booked them for a Moonlight cruise later that week.
There are other trips that you can do from here, so it is a great resort to meet the needs of relaxing and things to do. Further up river you come out at a lake which has thermal swimming and is peaceful and natural, worth a visit!
Unfortunately the hotel we stayed in has gone downhill since our last stay, so until some money is spent on bringing it back to a reasonable standard, I would not recommend it. However, there are plenty other hotels, apartments and villas to choose from in this lovely resort.