A lifejacket is an article of protective clothing that is designed to keep the wearer's head floating above the surface of the water. A lifejacket is technically referred to as a Personal Flotation Device or PFD. They are often brightly colored, like yellow or orange to maximize visibility for rescuers and some types have additional signalling devices such as whistles attached.

In some countries, they are compulsory on dinghies. On larger ships, it is a requirement to have at least the same amount of lifejackets on board as the number of people the ship will accommodate. Lifejackets are one of the security features required for boating. Aircraft that fly over water usually carry a life jacket for each passenger.

History

The history of the lifejacket can be traced back to simple blocks of wood or cork used by Norwegian seaman. The forerunner of the modern lifejacket is generally credited to a Captain Ward, a Royal National Lifeboat Institution inspector in the United Kingdom, who, in 1854, created a cork vest to be worn by lifeboat crews for both weather protection and buoyancy.

In World War II, the Allied soldiers wore the type B-4 inflatable lifejacket. They fondly nicknamed the jacket the "Mae West" as the jacket, once inflated, resembled, the buxom chest of the famous film star.

Specialised lifejackets

Specialised types of PFDs exist, such as shorter-profile vests used for kayak racing, very highly-buoyant types for river outfitters and other whitewater professionals. PFDs which include harnesses for tethered rescue work ('live-bait rescue') and pockets or daisy-chains for the attachment of rescue gear are made for swiftwater rescue technicians.

PFD's including 'wet' or 'dry'-suits are made that are intended for long term immersion in cold water. A flotation device known as the Steinke hood is used as an escape device to ascend from a stranded submarine.

The Mark 10 Submarine Escape and Immersion Equipment (SEIE) suit is intended to allow submariners to escape from much deeper depths than currently possible with the Steinke Hood. Some United States Navy submarines already have the system, with an ambitious installation and training schedule in place for the remainder of the fleet.

Because it is a full body suit, the Mark 10 provides thermal protection once the wearer reaches the surface, and the British Royal Navy has successfully tested it at six hundred foot depths. (see Submarines in the United States Navy#Pressure and escape training and Steinke hood)