Complex sentence: Billy elects to go down with his ship, the rest of the crew are trapped and only Bobby manages to surface as he watches the boat go under; however, without a life jacket, he has no chance of surviving.
Split into simpler sentences: Billy elects to go down with his ship, the rest of the crew are trapped inside and only Bobby manages to get out. He surfaces in time to watch the boat go under; however, without a life jacket, he has no chance of surviving.