As a ship moves through the water, it causes a wake, which is also moving forward relative to the sea. in addition to a fore and aft motion, this wake also has a (n)

upward and inward flow

Explanation:

The answer can be best explained by knowing what a "wake" is at first.

A wake is a disturbance in the flow of an object that is moving or immobile. For moving objects, they are influenced by the movement of the fluid. The disturbance of the flow could either occur behind a stationary body or a moving body due to the differences of density. Sometime, it is also caused by turbulence.

The wake in the statement above is caused by the second factor. The ship causes the displacement of water, which then in turn results to wake waves of both fore (the front of the ship) and aft (the rear of the ship). Besides these motions, it also causes an upward and inward flow. This is caused by the general rise of water as the stern (the back part of the ship) moves forward.