What does the hand signal 'thumbs up' mean?

The hand signal 'thumbs up' is universally recognized as a clear indication that everything is fine or that no issues are present. In the context of lifeguarding or aquatic safety, using this signal communicates to others that the situation is safe and that there is no immediate concern requiring attention. It serves as a quick and effective way to convey a positive status, ensuring that lifeguards and other personnel can quickly assess the safety of the environment without needing verbal communication.

In contrast, other signals would denote different messages, such as needing help or alerting to a specific situation requiring attention, which is why they do not apply in this context. The 'thumbs up' signal's simplicity and clarity make it an essential part of non-verbal communication in lifeguarding scenarios.