There are many different types and styles of PFDs. The following list provides a summary of advantages of the many types, and how many you will need, depending on the type of boat and the number of people on board.
 

Type I (Off-Shore Life Jacket) (22 lbs buoyancy)

• Where: Best for open, rough or remote water, where rescue may be slow in coming.
• Advantages: Floats you best. Turns most unconscious wearers face-up in water. Highly visible color.
• Disadvantages: Bulky
• Sizes: Two sizes to fit most children and adults.

Type II (Near-Shore Buoyant Vest) (15.5 lbs buoyancy)

• Where: Good for calm, inland water, or where there is a good chance of fast rescue.
• Advantages: Will turn many unconscious wearers face-up in water. Less bulky, more comfortable than Type I.
• Disadvantages: Not for long hours in rough water. Will not turn some unconscious wearers face up in water.
• Sizes: Infant, Child-small, Child-medium, Adult

Type III (Flotation Aid) (15.5 lbs buoyancy)

• Where: Good for calm, inland water or where there is a good chance of fast rescue.
• Advantages: Generally the most comfortable for continuous wear. Freedom of movement for water skiing, small boat sailing, fishing, etc. Available in many styles, including vests and flotation coats.
• Disadvantages: Not for rough water. Wearer may have to tilt head back to avoid face down position in water.
• Sizes: Many individual sizes from Child-small to Adult.

Type IV (Throwable Device)

• Where: For calm, inland water with heavy boat traffic, where help is always nearby
• Advantages: Can be thrown to someone. Good back-up to wearable PFD. Some can be used as seat cushions.
• Disadvantages: Not for unconscious persons. Not for non-swimmers or children. Not for many hours in rough water.
• Kinds: Cushions, rings, and horseshoe buoys

Type V (Special Use Device)

• Where: Only for special uses or conditions
• Advantages: Made for specific activity. Varieties include boardsailing vests, deck suits, work vests, hybrid PFDs and others.
• Disadvantages:  See label for limited use

Type V (Hybrid Device)

Required to be worn to be counted as a regulation PFD.

•  Advantages: Least bulky of all types. High flotation when inflated. Good for continuous wear.
• Disadvantages: May not adequately float some wearers unless partially inflated. Requires active use and care of inflation chamber.
• Performance level: Equal to either Type I, II, or III performance as noted on label.