NUC (Not Under Command)

COLREG Rule 3(f) defines a vessel Not Under Command (NUC) as one which through some exceptional circumstance is unable to manoeuvre as required by the Rules + is therefore unable to keep out of the way of another vessel. NUC vessels display two red all-round lights (or two black balls in daytime) per Rule 27(a). Under Rule 18(a) power-driven vessels must keep out of the way of NUC vessels. NUC is distinct from Restricted in Ability to Manoeuvre (RAM) — RAM covers vessels restricted BY THE NATURE OF THEIR WORK.