Happy as a Clam

Switches between two images: 1) image of a pink clam with closed mouth, positioned among aquatic vegetation and fishes, sea star, and sea horse. Black text centered on upper portion of button, white background. 2) The same, with the clam's mouth open, breathing out small, flower-like objects. Sea life in slightly different positions, as if swimming. 

The phrase "happy as a clam," as shown on the button, means to be exceedingly happy and content. Some suggest that it was because the shape of a open clam resembles a smile. The origin of the phrase may have come from the fuller version, now rarely heard, "as happy as a clam at high tide/water."  Clams can be dug up when the tide is low, and they are free from the attentions of predators when the tide is full, hence happy. The phrase originated in the north-eastern states of the USA in the early 19^th century. The expression became a common phrase by the late 1840s.