If necessary to attract the attention of another vessel
any vessel may make light or sound signals that cannot be mistaken
for any signal authorized elsewhere in these Rules, or may direct
the beam of her searchlight in the direction of the danger, in such
a way as not to embarrass any vessel. Any light to attract the attention
of another vessel shall be such that it cannot be mistaken for any
aid to navigation. For the purpose of this Rule the use of high intensity
intermittent or revolving lights, such as strobe lights, shall be
avoided.