A buoyancy aid keeps a conscious person afloat; a life jacket turns an unconscious one face-up.

Buoyancy is distributed evenly around the torso rather than concentrated at the chest.

That makes it comfortable and easy to swim in and removes the turning action.

For an active, conscious wearer it is the right trade.

For anyone who might be unconscious in the water it is the wrong choice.

The two are different products for different scenarios rather than different quality levels.

Watersports where the wearer is an active participant - kayaking, canoeing, dinghy sailing, paddleboarding and water skiing.

In all of those the wearer expects to end up in the water and is capable of swimming.

A jacket forcing them onto their back would be a hindrance.

Rescue swimming and safety boat crews use them for the same reason.

Supervised, close-to-shore activity by capable swimmers is the general case.

Commercial work over water generally points to a life jacket instead.

Yes - a paddler who cannot rotate cannot paddle, and a garment restricting swimming makes self-rescue harder.

Cut, armhole size and buoyancy placement all affect it.

Short-cut aids suit paddling because they clear the spraydeck and the seat.

Large armholes matter for repeated overhead arm movement.

A restrictive garment also gets loosened, which is worse than a comfortable one.

It is a genuine performance requirement rather than a comfort preference.

Snug enough not to ride up - lift at the shoulders and it should not slide past the ears.

An oversized aid rides up in the water and is close to useless.

Side adjusters and correct sizing are what achieve the fit.

Sizing is normally by chest measurement and by weight range together.

Children's aids in particular need checking as they grow rather than being handed down.

The shoulder lift test takes seconds and catches most fit problems.

Inspection rather than service - inherently buoyant foam has no mechanism to fail.

Foam can compress and degrade over years and with heavy use.

Stitching, buckles, zips and webbing are the components that fail.

Ultraviolet exposure degrades outer fabrics and webbing noticeably.

Rinsing after salt water use and drying before storage extends life considerably.

Any aid with damaged foam, failed stitching or a broken buckle is withdrawn rather than patched.

Generally not - commercial work usually specifies a life jacket because unconsciousness is a credible outcome.

A fall from height into water may cause injury or unconsciousness.

Cold water shock can incapacitate someone within seconds.

Working alone or at night removes the assumption that help is immediate.

Requirements differ by market and by industry and are frequently specific.

Where the applicable rules specify a jacket, a buoyancy aid does not satisfy them regardless of its buoyancy level.

Enough for the wearer's weight and clothing - and levels are stated rather than guessed.

Buoyancy levels are defined by the applicable standard and marked on the garment.

Heavier wearers and heavier clothing need more.

Cold water clothing such as drysuits changes the calculation considerably.

Rating schemes and level designations differ between markets, which catches people out when buying abroad.

The marking states which scheme it was certified under.