Complex sentence: The North Korean vessels attempted to board "Pueblo", but it was maneuvered to prevent this for over two hours and a sub chaser opened fire with a 57 mm cannon, killing one member of the crew.
Split into simpler sentences: The North Korean vessels attempted to board "Pueblo", but she was maneuvered to prevent this for over two hours. A sub chaser then opened fire with a 57 mm cannon, killing one member of the crew.