U1-2-3: Saltmarsh Trilogy
The Saltmarsh Trilogy comprises U1: The Sinister Secret of Saltmarsh, U2: Danger at Dunwater, and U3: The Terrible Title aka Final Enemy. These were released annually 1981-3. "U" stands for "United Kingdom". All three are credited to "Dave Browne with Don Turnbull" - why the preposition, maybe some Limey thing.
Anyway the series was all deemed good at the time. It got translated to a higher edition and fleshed out, and competently. So competently, we're not going to spoil it all here for a change. Refer to Ghosts of Saltmarsh.