A dozen or so meters was not very deep in open water. If they held their breath, they could swim up. Besides, both of them had life jackets. The moment they got out, they would start floating upward. As long as they held their breath, they would quickly reach the surface. The hijackers had already withdrawn.
This escape plan looked simple, but it had actually been extremely dangerous. It required the combined efforts of many parties; otherwise, it could never have succeeded.
First, the plane had to remain perfectly balanced. If it lost balance while sinking, its descent speed would rise exponentially. In other words, the plane had to sink flat in order to go down slowly. That was why, after the hijackers had waited around for so long, it had only sunk a dozen meters or so. If it had gone nose-first, that amount of time would have been enough for it to reach the seabed. In that case, survival would have been impossible. This was all thanks to the captain's exceptional emergency-landing skills.
Second, even at a depth of a dozen meters, the water pressure could not be underestimated. Under those circumstances, breaking the window and getting out was nearly impossible. But fortunately, Schiller had an extraordinarily powerful revolver. Forget a dozen meters of water pressure—even a hundred meters probably would not have stopped it. One shot shattered the glass, allowing them to swim out as quickly as possible.
Lastly, both of them were in decent physical condition. Although the captain was a little older, he had been a fighter pilot in his youth, one of the best among hundreds. Schiller was not in great shape, but this amount of exertion was still nothing to him. More importantly, both men had remained calm. They had forced themselves to