Happy as a Clam?

Well, my daughter's musings on the above phrase's meanings/origins directed me to a Google search where I found:

John G Saxe discussed the phrase poetically, in his Sonnet to a Clam, in the late 1840s:
Inglorious friend! most confident I am
Thy life is one of very little ease;
Albeit men mock thee with their similes,
And prate of being “happy as a clam!”
What though thy shell protects thy fragile head
From the sharp bailiffs of the briny sea?
Thy valves are, sure, no safety-valves to thee,
While rakes are free to desecrate thy bed,
And bear thee off,—as foemen take their spoil,
Far from thy friends and family to roam;
Forced, like a Hessian, from thy native home,
To meet destruction in a foreign broil!
Though thou art tender, yet thy humble bard
Declares, 0 clam! thy case is shocking hard!

The saying is very definitely American, hardly known elsewhere. The fact is, we’ve lost its second half, which makes everything clear. The full expression is happy as a clam at high tide or happy as a clam at high water. Clam digging has to be done at low tide, when you stand a chance of finding them and extracting them. At high water, clams are comfortably covered in water and so able to feed, comparatively at ease and free of the risk that some hunter will rip them untimely from their sandy berths. I guess that’s a good enough definition of happy.

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