The Village by the Sea — Paula Fox

When Emma's father goes to the hospital for surgery, she is sent to stay with Aunt Bea the "terror" and kindly Uncle Crispin. Emma wonders how she will survive two weeks with the always hostile Aunt Bea.

Luckily, Emma makes a friend, Bertie, and the two girls begin a project on the beach. Together they build tiny houses out of stones, shells, and all sorts of sea treasures. Here at the beach with Bertie, Emma finds comfort and friendship and takes pride in her carefully planned village.

Then one day Emma and Bertie's village is destroyed...