Katie Ledecky wins 16th world title in 800m freestyle.
She becomes first swimmer with six golds in one event at worlds.
Ledecky holds seven Olympic gold medals and two world records.
Always seeking improvement, never fully satisfied with her performance.
Kaylee McKeown of Australia sweeps all three backstroke events.
Sarah Sjöström of Sweden wins 50 butterfly, matching Phelps' record.
Zhang Yufei of China takes silver in 50 butterfly after 100 fly win.
Rikako Ikee, leukemia survivor, warmly welcomed by Japanese crowd.
Cameron McEvoy of Australia wins gold in 50 freestyle.