A buoyancy aid is a specific type of personal floatation device for inshore watersports. They are most commonly used for dinghy sailing, kayaking and canoeing and are designed with mobility in mind so that they don't restrict movement for the user.
They are floatation aids rather than lifejackets so should be used by those who can swim and have help close at hand.
A buoyancy aid will not turn an unconscious person from face down in the water onto their back.
There are different designs to choose from; side zip or front zip, elasticated or adjustable shoulder straps, single or multiple webbing straps with clip, with or without pockets.