Something as dramatic as a mechanical fish needed a dock that was worthy. I'm working on a storyline that explains the whole setup and as the story evolves, so too does the mechanical fish and dock. In the last days the back has been removed so I can do the rockwork and painting inside before final assembly.
I decided a cast iron drawbridge was in order. The submaarine would come into the subteranian carvern from an underwater entry. Because the carern occasionally floods the door to the control chamber is able to be latched tight agains the water pressure. When the submarine is docked and winched into place a cast iron drawbridge is lowered for access. Chains and lifting mechanism are still to be added.
Details abound already. The heavy 'cast iron' grate features the letter 'D' to signify the submarine is of the legendary D-CLASS.
More details to follow...