Life jackets should be compulsory for all recreational boaters, say experts, reporting on the differences in the death toll from boating incidents in Victoria, Australia, before and after legislation was introduced, in the journal Injury Prevention.
Recreational boaters make up a sizeable proportion of drowning deaths, not only in Australia, but in many other developed countries, warn the authors.
Voluntary agreements don't work, yet only two jurisdictions in the world have legislation in place, they point out.
The state of Victoria passed a law making life jacket wear compulsory for all recreational boaters in December 2005, following in the footsteps of Tasmania.
The law took into account vessel buoyancy and stability, recognising that any vessel less than 4.8 metres (15.7 feet) in hull length is particularly vulnerable to water swamping and capsize. The law applied to any open area of the boat except when it was at anchor, made fast to the shore, aground, or drifting.
Up to 2005, the regulations had required that all recreational vessels carry sufficient numbers of life jackets for every passenger should an emergency arise.
The decision to legislate was prompted by the poor impact of public safety campaigns and recommendations from coroners who observed the high numbers of drowning among recreational boaters, say the authors.
They looked at the annual number of drowning deaths reported by coroners among recreational boaters in the state's waters in the six years leading up to the legislation and in the five years after its introduction to see what impact it had had.
Fifty nine recreational boaters drowned between 1998 and 2004. But in the six years after the law came into force, the death toll fell to 16.
Nine of these people had not been wearing a life jacket. Among the five who were, the life jackets were not approved models in two cases, and in one case the jacket had been put on incorrectly.
There was a very significant fall in the number of drownings among people on small powerboats (4.8 m or shorter in length), and significant falls in deaths among those on boats powered by outboard motors or sails, and those up to the age of 59.
While the decline in deaths was evident for all types of waterway - enclosed, coastal, and inland - only the fall in deaths for those boating on inland waterways was significant.
Eleven of the 59 people who died before the law came into force had been wearing a life jacket at the time, but two were wearing it incorrectly, and two were not wearing a jacket designed for the relevant conditions.
The most common reason for drowning among life jacket wearers was a failure to raise the alarm quickly enough, leading to delays in search and rescue.
Other factors included sustaining a head injury, exposure to cold, being a weak swimmer, being alone on board, drinking alcohol, and being trapped beneath the vessel.
The authors calculate that the wearing of life jackets rose from 22% before the introduction of the legislation to 63% afterwards, and that the odds of someone in a small powerboat wearing a life jacket rose eight-fold.
"These findings provide further support for the adoption of a regulatory approach, supported by visible promotion and enforcement to increase the wearing of [life jackets] in other jurisdictions," they conclude.
Making life jackets compulsory for all occupants of boats under 6 metres (19.7 feet) in hull length, as is the case in Tasmania, would save even more lives, they add.