No. You will have to physically disconnect the flex and the wires when you are ready to move the dock. You also must have a disconnect where the new circuit starts. I would replace the existing receptacle and mount a small weather tight disco. You could use a 4x4 treated post and install the disco and receptacle on it. It would be easy to un-install the flex and wires from a disconnect. Since the circuit is protected by a GFCI breaker no other GFCI is required.
Check around and see what others on the lake have done in this regard. To give you an idea how others have done it. Ask if it was performed by a licensed electrician or contractor.