Complex sentence: Lastly, the rough currents of Myeongnyang made it difficult for anybody who fell overboard or jumped from sinking or burning ships to swim to shore; most of the Japanese in the water ended up drowning.
Split into simpler sentences: Lastly, the rough currents of Myeongnyang made it difficult for anybody who fell overboard or jumped from sinking or burning ships to swim to shore. Most of the Japanese in the water ended up drowning.