Spring tides are not the tides of spring as many Iandsmen suppose. They are the very high and very low tides which occur twice a month, with the new and the full Moon, when solar and lunar magnetism pull together to make the circumterrestrial tide wave higher than at other times. The opposite to the spring tide is the neap tide, halfway between these phases of the Moon; down East, in Maine, there may be as much as five feet difference in range between springs and neaps.
Spring tides are beloved by all who live by or from the sea. At a spring low, rocky ledges and sand bars which you never see ordinarily are bared; the kinds of seaweed that requires air but twice a month appear; sand dollars like tarnished pieces of eight are visible on the bottom. Clam specialists can pick up the big "hen" clams or the quahaugs, and with a stiff wire hook deftly flip out of his burrow the elusive razor clam. Shore birds-sandpiper, plover, and curlew-skitter over the sea-vacated flats, piping softly and gorging themselves on the minor forms of life that cling to this seldom-bared shelf.
Samuel Eliot Morison from Spring Tides