33 C.F.R. § 87.1 Need of assistance.
Title 33 - Navigation and Navigable Waters
The following signals, used or exhibited either together or separately, indicate distress and need of assistance: (a) A gun or other explosive signal fired at intervals of about a minute. (b) A continuous sounding with any fog-signaling apparatus; (c) Rockets or shells, throwing red stars fired one at a time at short intervals; (d) A signal made by radiotelegraphy or by any other signaling method consisting of the group . . . — — — . . . (SOS) in the Morse Code, (e) A signal sent by radiotelephony consisting of the spoken word “Mayday”; (f) The International Code Signal of distress indicated by N.C. (g) A signal consisting of a square flag having above or below it a ball or anything resembling a ball; (h) Flames on the vessel (as from a burning tar barrel, oil barrel, etc.); (i) A rocket parachute flare or a hand flare showing a red light; (j) A smoke signal giving off orange-colored smoke; (k) Slowly and repeatedly raising and lowering arms outstretched to each side; (l) The radiotelegraph alarm signal; (m) The radiotelephone alarm signal; (n) Signals transmitted by emergency position-indicating radio beacons; (o) Signals transmitted by radiocommunication systems, including survival craft radar transponders meeting the requirements of 47 CFR 80.1095. (p) A high intensity white light flashing at regular intervals from 50 to 70 times per minute. [CGD 81–007, 47 FR 16174, Apr. 15, 1982, as amended by CGD 89–024, 55 FR 3947, Feb. 6, 1990; CGD 94–011, 63 FR 5732, Feb. 4, 1998]
Title 33: Navigation and Navigable Waters
PART 87—ANNEX IV: DISTRESS SIGNALS
§ 87.1 Need of assistance.