Complex sentence: Water continues to flood the "Poseidon" and cause the on-board boilers and then the plutonium cargo to explode, killing Svevo and his men.
Split into simpler sentences: Water continues to flood the "Poseidon" and cause the on-board boilers to explode, which causes the cargo of plutonium to also do so. The "Poseidon" completely explodes, killing Svevo and his men.