When in or around water, it is important to wear the correct personal floatation device.
In general a life jacket should always be worn in an open boat such as a yacht or small powerboat.
If participating in a sailing dingy, windsurfing or canoeing you should use a buoyancy aid.
For information on levels of buoyancy, please visit www.nationalwatersafety.org.uk/member/projects/info/wg0407_lifejackets.pdf (PDF)
Don't forget that life jackets and buoyancy aids require regular servicing!