Instructions
Go to the water's edge at the beginning of Dragon Cove, and move your character onto the sunken statue. This will reveal the mallet. Collect the mallet and go to the next screen.
Push the crate here with the fisherman on top of it to the edge of the dock, then stand next to the gong that has been revealed by pushing the crate out of the way. Use the mallet on the gong. The sound of the gong will cause a fish to jump out of the water onto the fisherman's hook.
Talk to the fisherman, who will wake up and notice the fish on his hook. He will reel up the fish and give you the map piece in the mouth of the fish. Take the map piece and return to your vessel to leave Dragon Cove.