The sea is especially very cold in the North Atlantic. Here’s just how cold the Atlantic is.
A pilot was flying a small Cessna across the ocean. Along the trip he encountered stronger headwinds than expected, and ended up in a situation where he didn’t have enough fuel to reach dry land. He was going to have to ditch the plane in the ocean.
Fortunately he had plenty of time to figure this out, and he managed to locate an offshore oil rig he could get to. He radioed ahead to let them know he was coming. He made a perfectly controlled landing and touched down in the ocean just 500 meters from the oil rig. He was wearing a full body cold water immersion suit, but failed to zip it up all the way.
He died of hypothermia in the short time where the oil rig crew was running a tender out to him.
There’s also that advice about never leaving your vessel until you absolutely have to.
That’s a great story. Ocean survival courses teach the 1-10-1 rule. If you are immersed in cold water, it takes 1 minute for catch your breath and orient yourself. You then have 10 minutes of useful movement before your hands stiffen up, and one hour until you are fully incapacitated. And “cold” means water at 15C or less, which is typical of the north Atlantic.