Complex sentence: Witnesses at the start of the trip said later that they doubted she would make it without sinking, and in fact the pumps were running the entire distance and by the time they arrived, her sides were starting to break apart.
Split into simpler sentences: Witnesses at the start of the trip said later that they doubted she would make it without sinking. During the trip, the pumps were running the entire distance and by the time they arrived, her sides were beginning to break apart.