Preparing for Possible Cold Water Immersion
Your chance of surviving cold water immersion depends on having sufficient flotation to keep your head above water, controlling your breathing, having timely rescue by yourself or others, and retaining body heat.
Prepare for boating in cold water conditions by always wearing a secured life jacket. Also wear layered clothing for insulation. Equip your boat with a means for re-entry (ladder, sling, etc.) to use if you should fall into the water.
Of course, the best prevention is to take all measures necessary to avoid capsizing your boat or falling into cold water in the first place.