How Life Jackets Work

Selecting a Life Jacket

Life jackets are not one size fits all, nor does one life jacket fit every situation. Because the amount of buoyancy a person needs to remain afloat is dependent on his or her size, life jackets won't work if they don't fit.

Life jackets come in infant, child, youth and adult sizes, and they include a weight and chest measurement that is appropriate for that jacket. A life jacket should fit snugly so that you don't slip out of it. If a life jacket is too big and rides up, then it could obstruct your nose and mouth and keep you from breathing. If it's too small, the snaps and buckles might break.


It's important to ensure that each person has a life jacket that fits. Simply strapping a child into an adult's life jacket won't work because a child's body weight is distributed differently than an adult's. Since that additional weight is mainly in the head, infant life jackets have flotation collars to better support the head and keep it out of the water. Infant and child life jackets also usually come with a crotch strap to hold the jacket in place.

As we discussed in the previous section, some life jackets are better suited for sailing in rough waters than in calm waters. Similarly, some flotation devices are made differently for different boating activities. For example, jackets for fishermen and paddlers have larger armholes, while devices for kayakers might be shorter and less bulky.

Flotation devices designed for activities such as water skiing are impact-tested to ensure that they will survive hitting the water at a high speed. Water skiers should look for a flotation device that has been tested for impacts at 50 mph (80 kph). This means that the flotation device will withstand the impact of a fall at that speed and will keep you afloat. A life jacket might help cushion fall, but the testing only ensures that the impact won't break a zipper or seam. It does not guarantee any bodily protection (or that you won't crack a rib if you smack the water at 50 mph).

All of this information can be found on the flotation device's label:

If a person does a variety of boating, from sailing to waterskiing to deep-sea fishing, it may be necessary to buy more than one life jacket.

A life jacket should be tested for proper fit every year. To learn more about how to test a life jacket and how to maintain it properly, see the next page.