Any vessel with divers operating from it must always display signals by day or night to inform other vessel users.
The daytime signal for divers is an international Code Flag 'A', at least 750mm long and 600mm wide.
It should be placed to ensure all-round visibility.
During night diving, a vessel must show the international signal for a vessel restricted in its ability to manoeuvre.
These are three allround lights in a vertical line, top and bottom are red and the middle one is white.