In addition, Inland Rules stipulate that a high
intensity white light flashing at regular intervals from
50 to 70 times a minute may be used. There is no basis
in the Rules for the popular notion that our national
ensign, hoisted upside down, is a recognized signal of
distress. No man-of-war would ever subject the
colors to that indignity. But if you should see a private
craft with the ensign hoisted upside down, it may be
in distress and you should report it without delay.
SPECIAL SUBMARINE SIGNALS
The following signals, though not part of the Rules
of the Road, are prescribed for submerged submarines
in emergency situations involving rising to periscope
depth or surfacing.
1. A yellow smoke flare fired into the air from a
submarine indicates that the submarine is coming to
periscope depth to carry out surfacing procedures.
Ships should clear the immediate vicinity, but should
not stop propellers.
2. A red smoke flare fired into the air from a
submarine is a signal that the submarine is in serious
trouble and will surface immediately if possible. Smoke
flares of any color, fired into the air at short intervals,
mean that the submarine requires assistance. All ships
in the vicinity should stand by to give aid.
Restricted visibility is defined as anything that
restricts regular visibility to a degree that endangers
safe navigation. Many people think of restricted
visibility as just fog, but restricted visibility can be
caused by many other things; rain, smoke, heavy seas,