What type of PFD is designed to be thrown to someone in the water?

The type of PFD designed to be thrown to someone in the water is called a throwable PFD, commonly referred to as a throwable flotation device or rescue buoy. These devices usually come in the form of a buoy, ring, or cushion and are meant to provide immediate assistance to a person in distress. They are not worn but can be easily thrown to someone who needs help, allowing them to grab onto it for buoyancy and support until rescue arrives.