Uncoiled, is wound
To spring again;
The mind enmeshed
Laid straight in repose,
And the body refreshed
By feeding the rose–
These are but visions;
These would be
The grave's derisions,
Could the grave see.
Here is the wish
Of one that died
Like a beached fish
On the ebb of the tide:
That he might wait
Till the tide came back,
To see if a crate,
“Beached” has two meanings–To be “beached” is to be stranded out of a body of water, but it also means “to cause someone to suffer a loss.” [The fish has suffered greatly from the tide, which has beached it, perhaps how Millay feels at times] 
 To die “on the ebb of the tide” means to die slowly and gradually; the tide is the grim reaper, and the sea is Death. For a fish to be on an ebb gives us an image of a dead body. 

Moriturus