All the following is true except that（）.

A.in many places a counter current flows in opposition to the main current close to the bank
B.current can vary with depth of water and large deep draught ships can experience different current effects at differing parts of the hull tend to turn to the wind
C.as speed is reduced，the increased proportion of the ship's vector which is attributable to current will set the ship close to obstructions
D.when close to the berth in a head current，there is a danger that flow inshore of the ship becomes restricted and the ship is subject to interactive forces