Clam Bake

"Happy as a Clam"

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"Origin"

Why would clams be happy? It has been suggested that open clams give the appearance of smiling. The derivation is more likely to come from the fuller version of the phrase, now rarely heard - 'as happy as a clam at high water'. Hide tide is when clams are free from the attentions of predators; surely the happiest of times in the bivalve mollusc world."

Why not just say, I'm happy? Or, if you really want to go the prey/predator route, how about "I'm as happy as a zebra when it escapes a potentially deadly attack by a lion in the jungle." Or: "I'm as happy as a bee after it makes a sting but before it realizes that now it's going to die."