Automatic Life Jackets
These life jackets work on the principle that an element in the inflation mechanism reacts with water (in most cases this ia a pill/pellet that dissolves in water), automatically triggering the gas cartridge, which in turn inflates the air chambers of the lifejacket. Automatic Lifejackets are a popular choice due to the reassurances of an auto firing mechanism, ideal if you're knocked unconscious when you hit the water. Automatic Lifejackets will also have a manual inflation mechanism as well.
Check out the Force 4 Video - One of our best ever Lifejacket Offers - Seago 165N - Ideal for coastal sailing