On line and International workshop working through international learnings on surviving in cold water (- 12C)
Cold water temperatures increases the risk of drowning with hyperventilation and then failing to swim as the body extremities get colder.
Wearing a PFD (correctly fitted) and having a Personal Locator Beacon substantially increases your ability to survive.
Links:
[1] http://www.coastguardmana.org.nz/users/trevor-farmer