On a day on the beach? Why not get the little ones involved in an activity that is fun, creative, involves walking up and down the beach and is rewarding?
Why not build a mermaid in the sand!
I must admit I didn't take pictures as I went along but the steps are incredibly simple but effective!!!
First draw a simple outline, you could make it so one of your little one's lies down and then draw around their body or you could just do the outline by eye.
Then you need materials, see what is abundant on your beach, if there is a lot of driftwood you could make a driftwood tail, or if loads of different coloured seaweed you could use that (though be careful as often where there is seaweed there is also jelly fish!
For my mermaid I used blue slate, which had been rounded by the sea, and sea weed for her hair as well as a few shells, though I wish I could have found some large ones! Unfortunately the winter storms had smashed them all up.
When your done, stand back and admire!