46 CFR §25.25-13

1. (a)This section applies to vessels described in § 25.25-1 that engage in ocean, coastwise, or Great Lakes voyages.
2. (b)Each immersion suit carried in accordance with § 25.25-5(e), each life preserver, each marine buoyant device intended to be worn, and each buoyant vest must have a personal flotation device light that is approved under subpart 161.012 of this chapter.
3. (c)Each personal flotation device light required by this section must be securely attached to the front shoulder area of the immersion suit, life preserver, or other personal flotation device.
4. (d)If a personal flotation device light has a non-replaceable power source, the light must be replaced on or before the expiration date of the power source. If the light has a replaceable power source, the power source must be replaced on or before its expiration date and the light must be replaced when it is no longer serviceable.