The statute for Texas ports’ is here:
Sec. 61.003. DUTY TO ENGAGE PILOT. (a) A consignee having control of a vessel shall obtain a pilot to provide pilot services when the vessel is under way or otherwise moving on a river, bay, harbor, or port in this state unless the vessel is:
INDENT=2 documented as a United States vessel and licensed for and engaged in coastwise trade;
(2) a public vessel;
(3) of 20 gross tons or less;
(4) a motorboat registered in this state; or
(5) subject to Subsection (b), in distress or jeopardy.
[/INDENT]
The boarding locations for ships is fairly straight-forward - with tugs and barges things get a bit more complicated.
The biggest factor, as noted by several previous posters, is safety. Historically, it was extremely difficult (unsafe) to board a pilot on to a tug with a barge-on-a-wire proceeding offshore. The tug can’t effectively swing to make a lee as the pilot boat approaches, so the tow was asked to proceed cautiously to a location where the pilot boat could safely transfer the pilot. The ATBs offer a bit more flexibility but there used to be a strong opposition to putting a pilot ladder out on the barge. This reluctance seems to be waning but aren’t we sailors are slow to change our habits?
Ultimately, the pilot is working at the vessel’s request. If you arrive at a port and you aren’t comfortable with the boarding instructions given by the pilot boat, don’t hesitate to challenge it. Use the radio, explain your concern, and seek another solution.
While pilots are viewed as mouthy, cavalier assholes, the simple truth is this - they are charged to protect the waterway on which they are commissioned, and having a vessel pile up on a jetty because they didn’t heed the vessel’s request to be boarded at the actual pilot boarding station isn’t good for anyone’s business. Which is better? Listening to a pissed off pilot for a few hours or having a serious accident?
One other note: when I first started piloting I was told that the most dangerous thing I will do regularly is boarding/disembarking offshore tugs and barges. So far, this statement is very true.