Ocean currents are well defined and（）.

In modern fathometers the sonic or ultrasonic sound waves are produced electrically by means of a(n)（）.

A swift current occurring in a narrow passage connecting two large bodies of water which is produced by the continuously changing difference in height of tide at the two ends of the passage is called a(n)（）.

Cold water flowing southward through the western part of the Bering Strait between Alaska and Siberia is joined by water circulating counterclockwise in the Bering Sea to form the（）.

In shallow water，waves that are too steep to be stable，causing the crests to move forward faster than the rest of the wave，are called（）.

The ocean bottom that extends from the shoreline out to an area where there is a marked change in slope to a greater depth is the（）.

Radiation fog（）.

In a tropical cyclone，in the Northern Hemisphere，a vessel hove to with the wind shifting counterclockwise is（）.

The presence of stratus clouds and a dying wind will usually result in（）.

Steam fog is most likely to occur on the Mississippi and Ohio Rivers in（）.