billow – The swell on the ocean produced by the wind, or on a river or estuary by the tide or wind. More…
slack water, slack tide – Before any turn of the tide, there is a time of slack water or slack tide. More…
happy as a clam – Originally happy-as-a-clam-at-full-tide; it may refer to the fact that when the tide is full, nobody is digging clams. More…
tidy – Comes from tide, which in Old English meant “time period”; its original meaning was “timely, opportune.” More…