Lifejackets should be considered essential pieces of kit for any sailor or motorboater, to make certain that you're prepared for any situation that may arise out on the water.
What kind of lifejacket do I need? This depends on what sort of boat you're on or the activity you're doing.
Automatic Lifejackets. These life jackets work on the principle that an element in the inflation mechanism reacts with water (in most cases this is a pill/pellet that dissolves in water), automatically triggering the gas cartridge, which in turn inflates the air chambers of the lifejacket.
Due to the dangers of cold water shock, most people choose automatic life jackets so that if they fall in they don't have to concern themselves with activating the lifejacket.
Manual Lifejacket Inflation. These lifejackets work by operation from the user, the lifejacket will have a pull chord or string that needs to be pulled firmly, this fires a pin triggering the canister to inflate the lifejacket.
Manual activation prevents the possibility of false activation, which can be caused by a damp automatic mechanism or the wearer being hit by a large wave. Of course, manual activation will not work if you are unconscious and a user might find it difficult to operate if suffering from the effects of cold water shock.