Is it realistic?
I'm currently shooting an action film for people aged 18 and over. It's about a naval officer who is robbed by pirates, brutally beaten and stripped of his underwear. The pirates chain him to a huge rock, cut a hole in the ice and throw him into the hole. The rock cracks open at the bottom after 40 meters. The naval officer breaks free and swims to the surface, but the ice is frozen over. He swims down, picks up a rock, uses it to break the ice and pulls himself out of the water. He sneaks onto the pirate ship, takes a gun and shoots the pirates. Is it theoretically possible for a person to survive five minutes under ice when the water temperature is -36 degrees Celsius?
In addition to the other answers :
A mistake that is often seen in action films: if you hit under water, the arm is braked in such a way that the impact effect is practically zero.
Well realistic is something else, but it sounds quite funny.
LG
No, because water freezes at 0°C, salt water slightly deeper,
but at -36°C everything is water ice.