Nice post. Good story, too :-)
The Colregs may have changed since your incident.
I believe under the current Rules an anchored vessel may, indeed, give the danger/doubt signal (5 or more short blasts), under Rule 34. The course guide I am presently using to renew my license specifically says that an anchored vessel may sound the danger/doubt signal, as well as vessels underway in meeting, crossing or overtaking situations.
In restricted visibility conditions an anchored vessel sounds the normal 5-sec rapid ringing of the bell every minute and, if over 100 meters long, in addition sounds a gong rapidly for 5 seconds after ringing the bell. Optionally, all anchored vessels may also sound a whistle signal, Morse "R", one short, one prolonged, one short....to warn other vessels.
Not sure about the "U" signal. Can't find it in the current regs.
Last edited by btrayfors; 03-21-2007 at 08:11 PM.