Complex sentence: He swam across English Channel in 1994 when he was 13 years old and in the same year, he swam across 6 channels to break Mihir Sen's record of swimming across 5 channels in a calendar year.
Split into simpler sentences: He swam across English Channel in 1994 when he was 13 years old. The same year, he swam across 6 channels to break Mihir Sen's record of swimming across 5 channels in a calendar year.