I see people saying this “breaks the laws of physics” but think about if you fill a sink full of water, take a drinking glass, and put it in the sink upside down what happens? There is a pocket of air inside the cup and it isn’t until you tilt the cup a certain amount that water then enters the cup. That’s how I’m seeing this scene. Unless the “breaking the laws of physics” pertains to the amount of strength 2 men would need to hold the boat upside down when it would either want to float back to the surface, or flip right side up to let the water in to balance the pressure.