46 CFR §161.012-9

1. (a)If a light is a flashing light, its flash rate when first activated, or within five minutes thereafter, must be between 50 and 70 flashes per minute.
2. (b)Each light must—(1) Begin to shine within 2 minutes after activation; and
   1. (2)Within 5 minutes after activation be capable of being seen from a distance of at least one nautical mile on a dark clear night.
3. (c)Each light must be designed to operate underwater continuously for at least 8 hours at a water temperature of 15° ±5 °C (59° ±9 °F). However, if the light needs air to operate, underwater operation is required only for 50 or more seconds during each minute of the eight hour period.
4. (d)Each light must be designed to operate both in sea water and in fresh water.
5. (e)A light that concentrates its light beam by means of a lens or curved reflector must not be a flashing light.
6. (f)Each light must be designed to operate in accordance with this section after storage for 24 hours at a temperature of 65° ±2 °C (149° ±44 °F), and after storage for 24 hours at −30° ±2 °C (−22° ±4 °F).