Final answer:
The signal used to indicate that a diver is in the water and boats need to stay clear is a red and white diver down flag. This flag alerts boaters to keep a safe distance from the area where divers are present to reduce the risk of accidents or injuries.
Step-by-step explanation:
The signal or mark used to indicate that a diver is in the water and boats need to stay clear is a red and white diver down flag. This flag is also known as an Alpha flag or a scuba flag. It is typically displayed on a buoy or boat to notify other watercraft that there are divers in the area.
The diver down flag is important for the safety of divers because it alerts boaters to keep a safe distance, reducing the risk of collision or injury. By staying clear of the flagged area, boaters can help protect the divers underwater.
When the flag is displayed, boaters should slow down, maintain a safe distance, and avoid passing directly over the flag. It is essential for divers and boaters to understand and respect these signals to ensure everyone's safety in the water.