Sinking is usually unplanned ... even in the EU [actual emergency radio call transcript below]
"Mayday, mayday, mayday"
"Zis iz zee German coast guard Vhat iz your emergency"
"We are sinking"
"Vhat are you sinking about?"
Bottom line is you probably stand a better chance of survival if you don't fall into the cold water in the first place. ie don't sink to start with.