Complex sentence: The first four watertight compartments were filling rapidly with water, the boiler-man's tunnel connecting the firemen's quarters in the bow with boiler room six was seriously damaged, and water was flowing into that boiler room.
Split into simpler sentences: The first four watertight compartments were filling rapidly with water. Also, the firemen's tunnel connecting the firemen's quarters in the bow with boiler room six was seriously damaged, and water was flowing into that boiler room.