I don't often get the opportunity to watch and photograph Sanderlings but our short trip to Pacifica, Ca to see and photograph the Emperor Goose, gave me that chance. I very much enjoy watching them chase the receding wave to try to locate a small crustaceans or other edible in the water or sand before the incoming wave chases them back. After an energetic 20 or 25 minutes of feeding action, the entire flock of Sanderlings retreated to a drier area, just above where the waves were breaking to rest and take a short nap. As the waves came closer to their rest area, due to the rising tide, they eventually had to move higher up the beach to escape the incoming breakers. Since most of the napping birds were perched on one leg as they napped, they many times remained on one leg while hopping creating a very humorous sight as the flock hopped further up the beach while still huddled together.
This is another person's video showing Sanderlings hopping instead of running but you need to picture them grouped close together as a flock as they hopped further up the beach.