There is a lot of confusion on the difference between a life jacket and a buoyancy aid because both exist to help you float, however most buoyancy aids are simply aids which aid and assist you in the water. Life jackets are life saving devices which fully support you in the water. You can get foam life jackets eg: on planes or cruise ships but in our experience the majority bought from chandleries are buoyancy aids.

Buoyancy aids are an “Aid” intended to help you stay on the surface while treading water; it will not help you under all circumstances. If they are to be officially called a life jacket, foam products have to have 150N (150 Newtons) of buoyancy and a full collar to support your head and neck, they should be able to right a unconscious casualty if they are face down in the water.

If you are unconscious or unable to tread water, a buoyancy aid will keep a conscious person afloat with your help as they tend to only have 50N (50 Newtons) of inherent buoyancy instead of 150N required to support the weight of an adult.

Buoyancy aids cannot be guaranteed to turn an unconscious body over and it will not support your body in the water. 

Lifejackets, if properly worn and in good condition, are designed to keep your airways clear of water, even if you are unconscious or injured.  When they are inflated to sufficient buoyancy, either manually or automatically, they are able to turn your body over and bring your head and face out of the water, even when you are unconscious, keeping you protected.

If there is a facial splashguard fitted, this can be brought over your face to shield you from sea spray and inhaling the water in this way.

Buoyancy aids are great when worn inland waters when participating in water skiing, tubing or other water sports, when the wearer is in sight of the shoreline and will be continuously in and out of the water.