Say "MAYDAY MAYDAY MAYDAY" — three times
Say "This is [vessel name × 3]"
Say "MAYDAY [vessel name]" once more
Give your position (lat/lon, bearing and distance from landmark, or GPS)
Describe the nature of distress (sinking, fire, person overboard, medical emergency)
State number of persons on board
Give any other relevant information (vessel type, colour, taking on water)
Say "OVER" and wait for a response. If none, repeat from step 1.