Why is there always a small boat behind a large ship in the san francisco bay?

Question

why is there always a small boat behind a large ship in the san francisco bay?

It seems like if the small boat if being pulled by the large ship.

Is it because the ship is being escorted out of the bay?

Answer 1

It's possible that you're seeing the pilot boat (pilotage has always been required from the "SF" sea buoy on in, before and after the Cosco Busan debacle), but I sort of doubt it. Pilot boats don't generally follow ships, they just come alongside long enough to drop off/pick up the pilot, and leave. Most likely what you are seeing is an escort tug, and they probably have a single line on, directly to the stern of the ship. This affords a greater degree of maneuverability for the ship if it is needed, especially in a situation like coming through the Oakland Bay Bridge, or Golden Gate. There's also probably another tug near the bow, although that one may or may not have a line on.

One of the reasons people are likely to think they're seeing a pilot boat is that most of the escort tugs in the Bay area are run by Crowley Maritime, who happen to paint their escort boats white and red, which happens to be the traditional colors for a pilot boat. SF Bay pilot boats are yellow, with green trim.

Answer 2

After the oil spill a year or so ago (when the tanker hit the G.Gate bridge) all large vessels must have a pilot on board to go from the bay out to sea.  The small boat is the pilot ship which brings (and picks up) the bay pilot.  Once the ship is 'at sea', the pilot disembarks and the ships captain resumes control of the vessel.

.If you are close enough you will see the word "PILOT" written on the sides of the small boat.

.

Answer 3

It is probably the boat that will take the pilot off the ship after the ship clears the pilot required areas.

Answer 4

because if the small boat was in front of the large ship that would be dangerous