If memory serves, Dr. Giesbrecht defines cold water as anything below about 20 C (68 F). Survival time (with floatation) varies a lot, depending on body mass, gender, water temperature, etc. See the graph at http://www.coldwaterbootcamp.com/pages/1_10_60v2.html

In the case under discussion, water temperature clearly wasn't a major issue. The mere fact that they survived in the water for 14 hours demonstrates that. However, most places outside the tropics don't have water that warm. For the general case, water temperature is often (or usually?) a significant issue. Water that may be warm enough for a short swim could be lethal with long exposure.