Complex sentence: Crew members had little time to put on a life vest and jump to safety, over half the crew died from the explosions, sank with the ship or drowned when the support ships dropped depth charges to stop the submarine.
Split into simpler sentences: Crew members had little time to put on a life vest and jump to safety. Over half the crew died from the explosions, sank with the ship or drowned when the support ships dropped depth charges to stop the submarine.