National Maritime Museum, Falmouth, Cornwall

The Museum is housed in a modern purpose-built building on the waterside in Falmouth. Internally it is divided into a number of “zones” containing permanent or temporary exhibitions. Besides what’s on display, there are large archives and reserve collections. Unsurprisingly, the museum contains quite a lot of boats, and some more small craft of historic interest are moored at a pontoon outside. There is also a glass-walled tidal room in the basement when at the right state of tide one can see fish outside. There is a section of Cornish-related materials.
There is plenty to look at, though it can be a challenge to find one’s way around or, for instance, locate the walkway to the external pontoon. I remember the basement where I tried to photograph some fish through the glass wall. A museum visit can occupy several hours.
Parking nearby can be expensive. However if you park at the Ponsharden park + ride, you can take the “Park and Float” = parking + a boat trip to the quay near the Maritime Museum, qualifying you for discounted entry.
Also in Falmouth: Pendennis Castle.