A life jacket, also called a personal flotation device or PFD, is a buoyancy garment worn to keep a person afloat. Its job is simple to state and hard to do well: hold your airway clear of the water, even if you are unconscious, until you can be recovered. Beginners tend to think of a life jacket as something you grab when things go wrong. Experienced sailors know the opposite: the only life jacket that works is the one you were already wearing when you went over the side, and the modern inflatable designs that racers and offshore cruisers live in all day exist precisely so there is no excuse not to wear one.
How a life jacket works
Buoyancy is measured in Newtons in Europe and in pounds of flotation in the United States. A 50 N buoyancy aid helps a conscious swimmer but will not turn you face-up; dinghy sailors wear it because they expect to swim. A 100 N life jacket is the minimum for sheltered waters in light clothing, 150 N is the everyday standard for coastal and offshore sailing, and 275 N is for heavy foul-weather gear, where trapped air and waterlogged clothing fight against the flotation.
There are two families of construction. Inherently buoyant jackets use closed-cell foam and work without any action from the wearer, but they are too bulky to wear while grinding a winch. Inflatable jackets pack a folded bladder into a slim collar and fill it from a CO₂ cylinder, triggered manually by a toggle or automatically when a water-soluble bobbin or hydrostatic valve senses immersion. Most offshore sailors carry the automatic type, because the point is to work when you have just been knocked senseless by the boom.
Choosing the right jacket for the sailing you do
- Dinghies and small keelboats: a 50 N buoyancy aid gives freedom to hike and to swim back to a capsized boat.
- Coastal cruising: an automatic 150 N inflatable with crotch strap and whistle is the baseline for the whole crew.
- Offshore and ocean: a 150 N or 275 N automatic jacket with integrated harness, spray hood, light, retro-reflective tape and a pocket for an AIS beacon or PLB, as most offshore racing regulations require.
- Children: an inherently buoyant jacket sized by weight, with a crotch strap and grab handle, worn on deck, full stop.
On offshore jackets the tether clips to a D-ring on an integral webbing harness. Clip to the jackstay, not the lifeline, and keep the harness snug enough that you cannot slide out of it if you are dragged alongside.
Cruising vs racing
A cruising skipper sets a rule for when jackets go on and sticks to it: at night, in fog, when reefed, whenever anyone is alone on deck, and for everyone working forward of the mast. The rule removes the awkward moment of deciding whether conditions are “bad enough”. Racers usually have the decision made for them by the notice of race, which references World Sailing Offshore Special Regulations or a national equivalent, and by the fact that a modern racing PFD weighs less than a fleece. On a well-run race boat the jacket goes on with the boots and comes off with them.
Fitting, wearing and looking after it
Fit is the part most people get wrong. The jacket must be snug over whatever you are wearing, with the waist strap tight and the crotch strap fastened; without the crotch strap an inflated jacket rides up around your ears and can pull off over your head. The spray hood is not a gimmick – in breaking seas it is the difference between breathing air and breathing spray.
Service the jacket every season. Inflate it orally and leave it overnight to check for leaks, weigh the CO₂ cylinder against the stamped weight, replace the automatic firing mechanism before its expiry date, and check the light and whistle. Then repack it exactly as the manufacturer shows so the bladder can open without snagging. A jacket that has been sat on, left wet in a locker or repacked carelessly may not fire when you need it.
Frequently Asked Questions about Life Jackets
What is the difference between a life jacket and a buoyancy aid?
A buoyancy aid (around 50 N) helps a conscious swimmer stay afloat but is not designed to turn you face-up. A life jacket (100 N and above) is designed to right an unconscious person and keep the airway clear of the water.
Should I choose automatic or manual inflation?
For anyone who might go overboard unconscious, automatic inflation is the safer choice. Manual jackets suit dinghy and sportsboat sailors who expect to end up in the water deliberately and do not want the jacket firing at every capsize.
How often should an inflatable life jacket be serviced?
Inspect it yourself at the start of every season and after any immersion, and have it professionally serviced at the maker’s interval, usually every one to two years. Replace the cylinder and cartridge whenever they have fired or expired.
A life jacket does not make you a better sailor, but it buys you the time to be rescued by one. Choose the right buoyancy for your sailing, fit it properly, look after the firing mechanism and wear it as a matter of habit. Then get on with trimming the boat well enough that nobody ever has to test it.