As food retailers in the U.K. comer under increasing pressure to reduce their use of plastic, supermarket chain Co-Op is introducing compostable carrier bags in its stores.

To promote the move, it has a charming new spot out from agency Lucky Generals in which two older ladies who are real-life open water swimming enthusiasts are filmed taking a dip in the sea. The unscripted spot, directed by MJ Delaney at Merman, explains how making purchases at Co-op (including for products like its ice-cream) can reduce the amount of plastic pollution in the ocean.  It's part of the retailer's ongoing "It's What We Do" campaign, which highlights how the ethically-focused brand invests in communities. 

The Co-Op change comes as other retailers are trialing ways to cut down on plastic -- last week Waitrose said it would extend a trial of stores where customers are encouraged to bring their own containers for products such as pasta, vegetables and fruit.