Ships in a narrow channel are required to keep to the right side of the fairway, just like cars on the highway.

If you make a left turn in front of oncoming traffic, you will be hit on the starboard (right) side. In nautical rules of the road terms, the tanker was the "privileged" ship, it had the right of way. The destroyer was the "burdened" ship. It is up to the burdened ship to stay out of the privileged ship's way, the privileged ship is obligated to do nothing.

Needless to say, there are all kinds of regulations and rules that determine, in any meeting situation, who is burdened and who is privileged. And at night, ships are required to display colored lights that will give other ships information as to their orientation and direction. All ships carry navigation lights (red to port, green to starboard) and white lights (midships high, on the stern low), which will allow other ships to determine which direction they are moving at a glance, even in the dark.

Helm orders are given left and right, ("left full rudder") to avoid confusing the helmsman. The directions on the ship are given in terms of port(left) and starboard(right) from the bow. So if you are facing forward, the starboard side will be to your right. If you are facing aft, the starboard side will be to your left.

Of course, in the dark, when you're nervous or fatigued, people can get disoriented or be misunderstood and accidents happen.