On a Bali Scuba dive charter boat and most private boat, you may need to get help with the marine radio. Folloe the international protocol for getting help in an immediately life threatening emergency, non Bali Scuba diving :Turn the radio to channer 16, (hailing/distress channel)

Transmit mayday, mayday, mayday. This is … (give the boat name and registration number) Our location is … (give position by best mean possible, latitude/longitude or landmark). We have an injured scuba diver who needs immediate medical attention and we request assistance. Wait two or three minutes for a response before trying again.

Depending upon your location, local coast guard,  may respond. Alternatively, you may get responses from other boats prepared to help. Local authorities will refer you to another channel to continue communication to keep channel 16 clear. Repeat the designated channel and switch.After switching, transmit, (authority name), this is (your boat name). Always name whom you're calling first, who's you are second.Note that mayday distress call may only be used for life threatening emergencies.