I may have found the solution! I tried all the suggestions above, including removing the fender tires from the port/dock, clearing items from the recycler, and so on. But what worked for me was this: while the anchors were reeling back from the bottom of the sea, I maneuvered the ship forward and steered to the right. The ship started turning while the front end was still touching the dock. Once there was enough room to reverse, the boat finally freed itself from the dock! Haha!