The first version Batboats were sold with a little plastic "trailer coupling" that fit over the first version Batmobile's turbine exhaust (held by friction). This coupling provided a hook for pulling the trailer. Those trailer couplings are very rare these days. But at least the first version Batmobiles were able to pull around the Batboat and trailer.
The parts "rebuild" them same look as original.
BE CAREFUL !!!!
Left is rebuilt / Right is original