What is the main advantage of a type iv pfd? it is designed to be thrown to someone in trouble. it is very comfortable to wear. it has a lot of pockets. it provides good protection from cold water?

The best answer is :
                                  It is designed to be thrown to someone in trouble.

Type IV PFD refers to the fourth level of U.S. Coast Guard's (USCG) classification for private flotation devices. sort IV PFDs are carried on boats as a tool which will be thrown to a drowning person. Sort 4 PFDs also is referred to as a throwable float or sort four PFD.

This is a time line from 685 to 978