Turn down the 'water' setting to normal or low. It won't be perfect - but it will improve stuttering. From there, use V-sync in conjunction with freesync to smooth frame times.
You don't really want your GPU to be running full throttle constantly, especially for a CryEngine game - which perform a bit worse on AMD cards. Use a program like Riva Tuner to lock the frame rate to your monitor's refresh rate (e.g. A little late to this post, but just wanted to chime in as I've been having similar problems with Crysis 2.
