Statistics show that “nine out of 10 drownings occur in inland waters, most within a few feet of safety. Most of the victims owned PFDs [lifejackets], but they died without them. A wearable PFD can save your life, if you wear it. If you haven't been wearing your PFD because of the way it makes you look or feel, there's good news. Today's PFDs fit better, look better and are easy to move around in.”
U.S. Coast Guard information about lifejackets calls them PFDs (personal flotation devices), a term which is used in a “strictly regulatory sense” i.e. for writing regulations. Some CG literature and websites are being modified to say “wearable lifejacket” and “throwable device” to avoid confusion. In the U.S. “each PFD sold for use on a recreational boat is required to be provided with a guide to selection entitled ‘Think Safe – Choose the Right PFD’. These pamphlets are tailored to the kind of PFD to which they are attached.” Read the guides carefully when you are selecting a lifejacket, and make sure it is suitable for the kind of boating you do and for the person (adult or child) who will wear it.
“The Coast Guard is working with the PFD community to revise the classification and labeling of PFDs. When completed, this information will be updated and hopefully be somewhat easier to understand. Meanwhile, spending a few minutes to understand the many options available to find a PFD that you’re willing to wear could mean the difference between life and death for you or a loved one.” See this Coast Guard website for detailed information on PFD selection, use, wear, and care. www.uscg.mil/hq/cg5/cg5214/pfdselection.asp#recreational
Although this website talks about U.S. types of lifejackets, the general theory about what kind of lifejackets are suitable for offshore, near shore, for children, etc. applies to lifejackets sold in other countries. Check with the boating authorities in your country for specific requirements and guidance to find a lifejacket that you will wear.
[The quotes above come from the Coast Guard website.]