Chest harnesses - recent research has investigated the efficiency of quick release buckles: for the quickest release use the toggle on the buckle rather than the strap end; the strap end should be a short as possible. Be aware that release efficiency is related to the speed of the water - in slower flowing water it may be necessary to adopt a star position with arms and legs outstretched to create enough drag to be released.
Loose equipment - has been identified as a contributory cause to deaths on white water. Ensure all your kit is securely stored either in a buoyancy aid pocket or in your boat.
Incorrect assessment - incorrectly assessing either the grade of the river on that day or an over-optimistic assessment of a paddlers ability has also been a contributory cause to deaths on white water. Ensure you inspect the river and any crux rapids on the day and do not just rely on a guidebook. Listen to your mind and body - how are you paddling? Ultimately there is only one grading system that works, either yes or no: yes the water is right for the way I am paddling today; no this is not the river or rapid for me today.