When you go to look at model train shows you don’t often see boats or ships. I suppose this might be collecting or delivering freight from the train running alongside the quay.
We went to Weymouth several years ago and saw the metal train tracks embedded in the harbour quay. I guess they would have used it for loading fish and shellfish to take to cities like London. I think there are similar lines in Plymouth. I know they had large passenger ships calling in at Plymouth in the past and they still have a ferry service as does Weymouth. Transport is a fascinating subject.