Swimming weather

We went to the lake for a swim today and watched this family playing with their dog.  They initially threw a stick for him to retrieve but if he couldn't find it he would keep on swimming into the middle of the lake beyond reach of his owners and no amount of calling him would persuade him to come back to shore.  He was so intent on finding the stick.  So they changed to throwing this sandal made of rubber as it was bigger and easier for the dog to find.