The vessel should be displaying proper signals whenever dive operations are taking place from the boat. A vessel cannot be moved while divers are in the water. By the rules of navigation the vessel is restricted in its ability to maneuver and a hazard to navigation (Rule 27) . If this is a day operation, the vessel must display a rigid international code flag alpha, one meter in height from the top of the boat. This signal shows the vessel is restricted in its ability to maneuver. The sport diver flag is often flown under the code "A" flag. By doing this, you are instructing all boating traffic that you have underwater operations taking place, and your vessel is restricted in its operation.
For complete details read the text of Rule 27 (link below)
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