The Coast Guard identifies channel 16 as the international distress, safety and calling channel. A distress call should state MAYDAY, vessel identity, position, nature of distress, assistance needed and people aboard.
Speak slowly, repeat critical details and remain by the radio when possible. A responder may use the continuing transmission to help locate the vessel.
Channel 16 is not for routine radio checks or lengthy conversation. Move non-distress traffic to an appropriate working channel.