46 CFR §117.71

1. (a)An adult life jacket must be provided for each person carried on board a vessel.
2. (b)In addition, a number of child-size life jackets equal to at least 10% of the number of persons permitted on board must be provided, or such greater number as necessary to provide a life jacket for each person being carried that is smaller than the lower size limit of the adult life jackets provided to meet this section, except that:
   1. (1)Child-size life jackets are not required if the vessel's Certificate of Inspection is endorsed for the carriage of adults only, or
   2. (2)When all “extended size” life preservers (those with a lower size limit for persons of 1,195 millimeters (47 inches) in height or weighing 20.4 kilograms (45 pounds)) are carried on board, a minimum of only 5% additional child size devices need be carried.
3. (c)Each lifejacket must be approved under approval series 160.002, 160.005, 160.055, 160.155, 160.176, or 160.255 in subchapter Q of this chapter, or other standard specified by the Commandant. An inflatable lifejacket approved under approval series 160.255 must include a full back-up inflation chamber.
4. (d)Each life jacket carried on board the vessel must be marked in accordance with § 122.604 of this chapter.