Two divers, Bill and Tony, faced an accident while trying to take a selfie underwater. Bill had ten years of experience but lacked advanced training, leading to overconfidence. They dove to 120 feet and planned to enter a wreck but didn’t have enough air supply. Key lessons from their experience include planning dives properly, seeking necessary training, using safety lines, and keeping ego in check during dives. These points emphasize the importance of safe diving practices.