The international distress channel. Monitored around the clock by rescue coordination and by every vessel within range of you.
What to say on the radio
Hold the transmit button, speak slowly, and read this out. Repeat the whole call until someone answers.
After you finish, release the button and listen. Don't keep transmitting — rescue can't answer while you're talking.
Mayday or pan-pan?
Grave and immediate danger to life — sinking, fire, someone in the water, a serious injury. Rescue drops everything.
Urgent but nobody's life is at risk — engine dead in calm water, lost, low on fuel. Same channel, same format, say "PAN-PAN" three times instead.