Life jackets are also called Personal Flotation Devices or PFDs.
Under California law, every child under 13 years of age on a moving recreational vessel of any length must wear a Coast Guard-approved life jacket in serviceable condition and of a type and size appropriate for the conditions and the activity. The law does not apply to children under 13 years of age who are:
on a sailboat and are constrained by a harness tethered to the sailboat
in an enclosed cabin
on a vessel engaged in an emergency rescue situation
The following is a list of types of PFDs:
Offshore Life Jacket (Type I)
Best in open, rough or remote water where quick rescue may not be available. A Type I PFD will turn most unconscious persons face-up in the water and is highly visible. Approved for water skiing.
Near-Shore Buoyant Vest (Type II)
Good in calm, inland water, or where there is good chance of fast rescue. Type IIs will turn many, but not all, unconscious wearers face up in the water, but Type IIs are not suitable for long hours in rough water. Approved for water skiing.
Flotation Aid (Type III)
Good in calm, inland water, or where there is good chance of fast rescue. Generally the most comfortable PFD. Type IIIs are not good for use in rough water and the wearer may have to tilt head back to avoid being positioned face-down in water. Approved for water skiing.
Use in calm, inland water with heavy boat traffic where help is always nearby. Type IVs do not help unconscious persons, and are not designed for non-swimmers or children. Type IVs are not suitable for many hours in rough water. Not approved for water skiing. Required to be immediately available on all vessels 16 ft. and over.
Special Use Devices (Type V)
High flotation when inflated. Good for continuous wear. However, may not adequately float some wearers unless PFD is partially inflated. Type Vs must be used according to approved conditions listed on the label. Type Vs should not be worn during high-speed activities unless tested for those conditions. Not all Type V PFDs are inflatable.