Men's 1500m Freestyle
· Sun Yang (CHN) won this event at the World Championships in both 2011 (Shanghai) and 2013 (Barcelona).
· Two years ago, Sun had to forfeit the final of this event after suffering a physical setback in his warm-up. The world title was won by Gregorio Paltrinieri (ITA).
· Sun is one of three men who has won multiple world titles in this event. Grant Hackett (AUS) won it four times and Vladimir Salnikov (URS) won it twice.
· Coming into this tournament, Sun was already the only Asian man to have won an event three times at the World Championships, the men's 800m freestyle.
· At the Rio 2016 Olympic Games, Sun fell more than five seconds short of the top eight in the heats and thus missed the final of this event. He had won gold in the men's 200m freestyle and silver in the men's 400m freestyle in Rio.
· Once again, this paved the way for Paltrinieri who took the Olympic gold medal ahead of Connor Jaeger (USA) and countryman Gabriele Detti (ITA).
· At each of the last four world championships in a post-Olympic year, the men's 1500m freestyle was won by the reigning Olympic champion: Hackett in 2001 and 2005, Oussama Mellouli (TUN) in 2009 and Sun in 2013.
· The last time the reigning Olympic champion in the men's 1500m freestyle did not win gold at the next world championships was 1998 when 1996 Olympic champion Kieren Perkins (AUS) did not win.
· This is the only of the six individual men's freestyle events in which a world record was registered after 2009. Sun swam the current world record in this event at the London 2012 Olympic Games.
· The world record is Sun's since the 2011 World Championships in Shanghai, where he improved the mark by Hackett. The Australian had held the world record for 10 years.
Women's 50m Freestyle
· Bronte Campbell (AUS) will be trying to defend her world title in the women's 50m freestyle. Only Inge de Bruijn (NED, 2001-2003) and Libby Trickett (AUS, 2005-2007) have achieved this.
· Campbell and Ranomi Kromowidjojo (NED, won in 2013) can both equal De Bruijn and Trickett on a record two world titles in this event.
· Kromowidjojo also claimed two silver world championships medals in the 50m freestyle, in 2011 and 2015. She could join Therese Alshammar (SWE, G1-S3-B0) and Marleen Veldhuis (NED, G0-S1-B3) on a record four medals in this event.
· In each of the last eight editions of the world championships there has been a Dutch swimmer on the podium in the women's 50m freestyle, grabbing nine medals in total in this span (G3-S3-B3).
· Pernille Blume (DEN) won the 50m freestyle at the Rio 2016 Olympic Games. She can become the fifth woman to win the world title as the reigning Olympic champion, after Kromowidjojo (London 2012, world title 2013), Britta Steffen (GER, Beijing 2008, world title 2009), De Bruijn (Sydney 2000, world title 2001-2003) and Amy Van Dyken (USA, Atlanta 1996, world title 1998).
· Sarah Sjöström (SWE) is hoping to become the third woman with a world title in both the 50m freestyle and 50m butterfly, after De Bruijn and Alshammer. In 2015, she finished third and in 2013 fourth in this event at the World Championships.
· Simone Manuel (USA) took home the silver medal in the 50m freestyle from the Rio 2016 Olympic Games. Only Van Dyken, gold in 1998 and bronze in 1994, and Leigh Fetter (USA), silver in 1991, claimed a world championships medal in this discipline for the United States.
Men's 50m Backstroke
· Camille Lacourt (FRA) won this event at each of the previous two world championships.
· At the 2009 and 2011 world championships, this event was won by Liam Tancock (GBR).
· Lacourt and Tancock are the only swimmers who have won two world titles in this event.
· Tancock's winning time of 24.04 at the 2009 world championships in Rome still ranks as the world record in this distance.
· Lacourt clocked the second-fastest time ever at the 2010 European Championships that were held in Budapest, 24.07.
· In 2015, Lacourt became the first swimmer aged 30 (or older) to win this event at world championships.
· The youngest swimmer to win this event was Aristeidis Grigoriadis (GRE) at 19 in 2005.
· Lacourt has won three medals in this event at world championships. Tancock and Gerhard Zandberg (RSA) lead the way on four.
· France, Great Britain, Australia and South Africa have all won four medals in the men's 50m backstroke.
· Justin Ress (USA) and Matt Grevers (USA) hope to win the first gold medal for the UNited States in this event since Randall Bal won the first world title in 2001.
· Grevers took silver in the men's 50m backstroke at the last two world championships.
Women's 50m Breaststroke
· Reigning women's 50m breaststroke world champion, Jennie Johansson (SWE), could join Luo Xuejuan (CHN), Jessica Hardy (USA) and Yuliya Efimova (RUS) on a record two world titles in this event.
· Only Xuejuan won her two world titles in back-to-back championships (2001 and 2003).
· Xuejuan is the only Asian woman to finish on the podium in the 50m breaststroke at the world championships.
· Efimova finished on the podium of the 50m breaststroke in each of the last four editions of the world championships. She won the world title in 2009 and 2013 while claiming silver in 2011 and bronze in 2015.
· She shares the record of four world championships medals in this event with Hardy (G2-S1-B1).
· Ruta Meilutyte (LTU) is the current world record holder (29.48) which she recorded in the semi-final heats of the 2013 world championships en route to her only medal in this event (silver).
· Meilutyte became the youngest medallist in this discipline when she claimed her silver medal in 2013 at the age of 16.
Mixed 4x100m Freestyle Relay
· The mixed 4x100m freestyle relay event was first held at the world championships in Kazan in 2015.
· The first world title was won by the United States, ahead of Netherlands (second) and Canada (third).
· The only relay events in which the United States won each of the first two world titles are the men's 4x100m freestyle and the men's 4x100m medley.
· Simone Manuel (USA) is the reigning Olympic champion in the women's 100m freestyle, while Nathan Adrian (USA) finished on the podium at three of the last four men's 100m freestyle events at the Olympic Games and world championships combined. Both were part of USA's winning squad in 2015.
· Netherlands are the reigning European champions in the mixed 4x100m freestyle relay. The only relay event in which they have won a gold medal at the world championships is the women's 4x100m freestyle (2009, 2011).
· Ranomi Kromowidjojo (NED), 2012 Olympic gold medallist in the women's 100m freestyle, was part of both those winning Dutch teams and also claimed the silver medal with Netherlands in this event in 2015.
· Coming into these world championships, Canada has never won a world title in any relay event.
· Italy finished in second place in this event at the 2016 European championships - in 2015, they finished fifth place at the World Championships.
· Australia, China and Russia are among the countries that have yet to win a medal in a mixed relay event at the World Championships.