This title was the sixth of the original Pugwash series.  It was published by The Bodley Head as a colour picture book in 1976 and reprinted in 1993.

In an old Spanish fort, on Cactus Island in the Caribbean, Cut-throat Jack and his ugly crew are having a party. Little do they suspect that their archenemy Captain Pugwash is menacingly close by and that advancing through the water at an alarming pace is an extraordinary sea monster! Nothing goes quite according to Pugwash’s plan but all ends happily with only a bit of help from Tom the cabin boy!