Either a high water consisting of two maximums of about the same height separated by a relatively small depression or a low water consisting of two minimums separated by a relatively small elevation. This has also been called a double high water, an agger, and a gulder.
(Also known as agger, gulder.) A double-headed tide with a high water consisting of two maxima of similar height separated by a small depression (double high water), or a low water consisting of two minima separated by a small elevation (double low water). Examples occur at Southampton, England, along the coast of the Netherlands, and off Cape Cod, Massachusetts.