It's amazing how many interpretations of this joke people appear to have :) To me it's very clearly about Gilbert's past remarks that he'll never do another Mo

It's amazing how many interpretations of this joke people appear to have :) To me it's very clearly about Gilbert's past remarks that he'll never do another Monkey Island unless he fully owns the IP. Tossing Murray into the water means "yes, I don't own the IP and yet I'm making another Monkey Island, you can stop pointing it out".