There is a subtle difference between
1. I heard him leave and
2. I heard him leaving
I feel that in 2 the leaving is more imperfective in aspect, and in 1. more perfective in aspect. In other words, in 2. the visual image is the process of leaving, in 1. the point is that he left.
Interestingly, in the original sentence, there are three possibilities
I saw you ship blowing up (I was watching it as it happened)
I saw your ship blow up (I was present when it blew up)
I saw your ship blew up (I read about it in the newspaper/heard about it afterwards)