Complex sentence: The 2014 South Korean ferry capsizing refers to an event when the South Korean vessel "Sewol" capsized off South Korea as it was carrying about 459 people, mostly secondary school students from Danwon High School, from Incheon to Jeju.
Split into simpler sentences: The 2014 South Korean ferry capsizing was the capsizing of the South Korean vessel "Sewol". It was carrying about 459 people, mostly secondary school students from Danwon High School, from Incheon to Jeju.