Lake Koycegiz is beautiful and is in the Dalyan area. You can hire private boat which i would recomend or join a day trip, sometimes very crowded, depends on what you like.
Dalyan is really loverly, very flat, scenic with has a gorgeous river running through were you can take a walk and chill out.
There are lots of nice places to eat and stay, some nice shops. You can jump the dolmus to other nice places or take organized trips.
We love the area returned July going back Sept, if there is anything in particular you wish to know pm me, Joan