Type II is a little less buoyant and may not be designed to turn someone face up. A Type III life jacket is intended to help a conscious person stay afloat. Type I is rated for all types of waters ...

A former section chief of Minami-Sanriku town who lost his colleagues in the twin tragedies thought that a life jacket equipped with a GPS function could help quickly locate people swept offshore ...

There are two forces acting on the life jacket - its weight and the force ... Things that float are buoyant. If the weight is greater than the upthrust, it sinks.