Cook's chart with a twist

We found this print in the back of a drawer, it looks like a proof for a print that was never produced back in the day.  It is the classic Bayly version of Captain Cook's chart of New Zealand with some playful additions, a sea serpent, a whale and a sailing ship. It does not have a number on it, just the space for where it would have been hand-numbered had it been published.  We suspect it was an idea for a print that never went ahead and we haven't seen one anywhere else. One only.