In the sport of swimming, drag is a swimmer's worst enemy. Measures are taken, especially at meets, to reduce the disadvantages of drag, but the "suit era" of 2008-09 took this idea to new heights.
After slipping on these full-body polyurethane suits, such as the original Speedo Fastskin LZR or the Arena X-Glide, swimmers saw an 8 percent reduction of drag during their races. During the 2009 World Championships (held in Rome) alone, an astonishing 20 new world records were set.
While these suits were banned from the Olympics following the Beijing Games in 2008, a few of the era's records still haven't been touched to this day.
So which suit-era records have proven the most difficult to break?
200m Freestyle -- 1:42.00 (Paul Biedermann, Germany, 2009 World Championships)
Germany's Paul Biedermann, perhaps the biggest winner from the supersuit era, claimed the 200m and 400m freestyle world records at the 2009 World Championships in Rome. Of his two records, the 200 is without a doubt further from reach. Sun Yang has come agonizingly close to bettering Biedermann's 3:40.07 mark in the 400, missing it by just 0.07 seconds at the London Olympics.
The 200, on the other hand, has not even been threatened. Yang, Rio's gold medalist in the 200, was over 2 1/2 seconds from Biedermann's mark of 1:42.00. Michael Phelps is the only other swimmer in history to be under the 1:43 mark, with his 1:42.96 performance in Beijing, where he set the world record only to have Biedermann lower it by 0.9 of a second the following year.
Yannick Agnel's 1:43.14 at the 2012 London Games is arguably one of the most impressive 200 freestyles ever swam, yet still falls over a second short of Biedermann's mark. Since 2009, the next fastest performance is a 1:44.44 from Ryan Lochte at the 2011 World Championships -- 2.44 seconds slower than the record time!
200m Butterfly -- 1:51.51 (Michael Phelps, United States, 2009 World Championships)
Phelps' 1:51.51 200m butterfly from Rome is also staggering. The next fastest performance in history by someone not named Michael Phelps is Laszlo Cseh's 1:52.70 from Beijing. Despite young talent in this event (Chad le Clos, Masato Sakai, Tamas Kenderesi), this record doesn't appear to be going anywhere anytime soon.
200m Backstroke -- 1:51.92 (Aaron Peirsol, United States, 2009 World Championships)
Aaron Peirsol's 1:51.92 200m backstroke at the 2009 World Champs was so impressive that hardly anybody remembers Ryosuke Irie, only 19 at the time, also touching under the previous world record at 1:52.51. In Rome, Peirsol lowered Ryan Lochte's mark from Beijing of 1:53.94 by over two seconds to reclaim sole dominion over the record that he previously shared with his American teammate (Peirsol equaled Lochte's 1:54.32 at the 2008 Olympic Trials). Despite the emerging stardom of Mitch Larkin and Ryan Murphy, as well as the veteran Irie still in the game at 27 years old, this record remains tough to take down.
The women's side is a bit of a different story, as less of the record board is occupied by the supersuit-era records, and of those remaining, almost all seem poised to make an exit. Canada's Kylie Maase, at just 21, has already touched within a tenth of Gemma Spofforth's 100m backstroke mark of 58.12. Sarah Sjöström has multiple near misses on Britta Steffen's 50m freestyle mark of 23.73 with a couple of 23.8s and 23.9s. Federica Pellegrini's 1:52.98 in the 200m freestyle has shown staying power, but Katie Ledecky dropping 0.8 of second from her 2016 mark in the near future is not out of the question.
200m Butterfly -- 2:01.81 (Zige Liu, China, 2009 National Games)
The one women's record that appears to be devoid of recent competition is Zige Liu's 2:01.81 in the 200m butterfly from 2009.
That year proved to be a battleground for the women's 200 fly, as Mary DeScenza set the world record at 2:04.14 in the prelims at Rome, only for Jessicah Schipper to steal it in the finals and lower the mark to 2:03.41. This was all vain, however, as Liu went on to drop a 2:01.81 less than three months later in Jinan, China. Liu herself has not been able to touch that time -- her fastest time since is 2:04.40 in 2011 -- and hasn't been able to claim the No. 1 spot in the world in her signature event since 2011.
The suit era produced a deluge of new world records, many of which stand today. Among them, a few stand out as especially hard to beat. The women's most dominant suit-era record belongs to Zige Liu and her 200 fly from 2009. Good arguments can be made for a few records on the men's side, but we'll give the nod to Paul Biedermann's 200 free due to how far anyone is from threatening it.