Forty per cent of people in East Anglia don't know to call 999 for the Coastguard when an emergency happens at the seaside.
And Maritme and Coastguard Agency (MCA) reseearch shows that in some parts of the UK more than half of people still don't know who to call.
In a campaign to get the message across, the agency has recreated the kind of thank you messages it receives from people who are alive today because someone knew the right thing to do.
The 30-second video tells the story of a man who was cut off by a tide and how grateful he was that someone knew what to do.
Peter Mizen, assistant director, head of Coastguard operations at the MCA, said: "If you're in difficulty along the coast or at sea, every second will count so it's really important to know how to get hold of the right emergency service immediately."
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