“Don’t cry wolf!“
Relating the quote to the story
Crying wolf means calling out for help just for fun, without a reason. When the yachts send up flares for fun, George rushes over to help. However, there is no emergency there. When a yacht sends up a flare asking for help, George thinks that they are still having fun and does not go to rescue them. Crying wolf can put lives in danger, because when help is actually needed, no one will turn up, just like in the story.