INLET. (1) A short, narrow waterway connecting a bay, lagoon, or similar body 

 of water with a large parent body of water. (2) An arm of the sea (or 

 other body of water) that is long compared to its width and may extend a 

 considerable distance inland. See also TIDAL INLET. 



INLET GORGE. Generally, the deepest region of an inlet channel. 



INSHORE (ZONE). In beach terminology, the zone of variable width extending 

 from the low water line through the breaker zone. Also SHOREFACE. (See 

 Figure A-1.) 



INSHORE CURRENT. Any current in or landward of the breaker zone. 



INSULAR SHELF. The zone surrounding an island extending from the low water 

 line to the depth (usually about 183 meters (100 fathoms)) where there is a 

 marked or rather steep descent toward the great depths. 



INTERNAL WAVES. Waves that occur within a fluid whose density changes with 

 depth, either abruptly at a sharp surface of discontinuity (an interface), 

 or gradually. Their amplitude is greatest at the density discontinuity 

 or, in the case of a gradual density change, somewhere in the interior of 

 the fluid and not at the free upper surface where the surface waves have 

 their maximum amplitude. 



IRROTATIONAL WAVE. A wave with fluid particles that do not revolve around an 

 axis through their centers, although the particles themselves may travel 

 in circular or nearly circular orbits. Irrotational waves may be 

 PROGRESSIVE, STANDING, OSCILLATORY, or TRANSLATORY. For example, the 

 Airy, Stokes, cnoidal, and solitary wave theories describe irrotational 

 waves. Compare TROCHOIDAL WAVE. 



ISOBATH. A contour line connecting points of equal water depths on a chart. 



ISOVEL PATTERN. See HURRICANE WIND PATTERN. 



ISTHMUS. A narrow strip of land, bordered on both sides by water, that 

 connects two larger bodies of land. 



JET. To place (a pile, slab, or pipe) in the ground by means of a jet of 

 water acting at the lower end. 



JETTY. (1) (United States usage) On open seacoasts, a structure extending 

 into a body of water, which is designed to prevent shoaling of a channel 

 by littoral materials and to direct and confine the stream or tidal 

 flow. Jetties are built at the mouths of rivers or tidal inlets to help 

 deepen and stabilize a channel. (2) (British usage) WHARF or PIER. See 

 TRAINING WALL. 



KEY. A low, insular bank of sand, coral, etc., as one of the islets off the 

 southern coast of Florida. Also CAY. 



KINETIC ENERGY (OF WAVES). In a progressive oscillatory wave, a summation of 

 the energy of motion of the particles within the wave. 



A- 18 



