The following safety information has been kindly supplied by RNLI:
Given the circumstances in which people find themselves in the water, often without the time to don a lifejacket, it makes sense to wear one all the time. A correctly fitted lifejacket will keep you afloat long enough for those nearby to rescue you, or even until the arrival of search and rescue services.
Of all the bodies that the RNLI have pulled from the water, precious few were wearing lifejackets. If they had been, they would have survived longer, perhaps long enough to be found alive.
Choose a lifejacket that fits comfortably over your normal boating clothes and is fully adjustable. Spend time adjusting the straps so that you can place your fist between the buckle and yourself with no other gaps. Too big a gap and the lifejacket will be loose when in the water; too small a gap may be uncomfortable. Look for additions such as a spray hood, a light, a whistle and crotch straps.
The buoyancy of a lifejacket is measured in Newtons (N) and there are three common classes:
100N: designed for sheltered use and/or weak swimmers. Will not turn an unconscious casualty face-up.
150N: designed for coastal sailing and, if fitted correctly, will turn an unconscious casualty face-up.
175N: designed for offshore use and/or use with a lot of clothes.