The U.S. Coast Guard issued a Safety Alert reporting
various problems with floating electric waterlights. Sometimes replacement batteries are used that are too heavy, causing the lights to sink. Other times, the batteries are not installed properly or the flotation foam is misplaced. A bracket is sometimes used that is not designed for that particular light, with the result that the light may not properly release. Lanyards may deteriorate due to sun damage. Floating electric waterlights should be examined to ensure proper operation when needed.
Source: HK Law