happy as a clam (at high tide)

happy as a clam (at high tide)

Delighted with one’s lot. An American expression dating from the early nineteenth century, it comes from clamming, which involves digging clams out of the sand at low tide. At high tide it is difficult, if not impossible, to dig for clams. Safety thus is the obvious reason for the mollusk’s carefree state of mind.
See also: clam, happy, high