DICTIONARY OF

Undertow 370 Unrig
Undertow. Water flowing to seaward under surf.
Underwater Body. That volume of a vessel's hull that is immersed at a given draught.
Under Way. Not attached to the shore or the ground in any manner. Usually, but not
necessarily, moving through or making way through the water.
Under Weigh. Under way.
Underwriter. A person who insures, wholly or in part, a marine risk by stating the amount
for which he is liable in the policy, and then signing the policy. Underwriters at Lloyd' are
required to deposit, with Lloyd's, securities to the value of, at least, £5000.
Underwriting. Contracting to make good, wholly or in part, a marine loss; signing to this
effect at the foot of a policy of marine insurance.
Undulation. A rising above and a falling below a mean level in the manner of a smooth
wave, or ripple.
Undulatory. Having an up and down movement, together with a sidewise movement, but
without any translation of the particles of the fluid.
Unfurl. Cast loose a sail by letting go the gaskets.
Uniform System of Buoyage. Buoyage system in which the shape and/or colour of any
buoy or beacon has a definite significance. Most maritime nations have a uniform system of
their own. International system introduced in 1977.
Union. The device in the upper canton of an ensign or flag. Short name for the Union Jack,
or the stars device of U.S.A. ensign.
Union Flag. Union of an ensign when flown by itself.
Union Hook. Swivelled cargo hook with ring carrying two swivels for connection to the two
runners of a union purchase.
Union Jack. Device for a flag that forms the inner upper canton of a national ensign, or is
used separately. Particularly applied to the British jack, which contains the crosses of Saints
George, Andrew, and Patrick.
Union Purchase. Method of rigging cargo derricks so that they need not be moved while
loading or discharging a hatch. One derrick plumbs the hatch, the other derrick plumbing the
loading or discharging point overside. Runner of each derrick is shackled to the same cargo
hook. Precision in plumbing results.
Universal Rating Rules. Measurements of yachts over 15 metres (49.2 ft.) L.W.L. Adopted
in United Kingdom, 1931.
Universal Yacht Signals. Code of signals for yachts, produced by G. H. Ackers, 1847.
Revised 1851 and 1859. Fell into disuse soon after the introduction of the "Commercial
Code' of 1857.
Universal Time. Alternative name for 'Greenwich Mean Time'.
Unload. To discharge, or remove, cargo.
Unmoor. To cast off hawsers by which a vessel is attached to a buoy or wharf. To weigh
one anchor when riding to two anchors. To remove a mooring swivel when moored to two
cables.
Unrig. To remove rigging. To take off tackling or fittings.