During the advert, the crew of the Southport Lifeboat can be seen hauling a colleague out of the sea into one of their rescue dinghies.
The charity, which was founded in 1988, is independent of the RNLI and relies on donations to keep going.
Co-op's 5+1 membership scheme gives shoppers 5% back on their shop and 1% to good causes, some of which appear in the advert.
So far it has raised £1.4 million for more than 4,000 nominated charities.
The full advert will be shown first on ITV on December 1.