Is Drafting In Lap Swimming Possible?
The photo on the left, from the 2008 Beijing Olympics 4x100 meter relay was one of the most spectacular events in swimming history. Jason Lezak, the anchor leg of the American Relay overcame a seemingly impossible gap to out touch France's Alain Bernard to win the Gold medal. Lezak's 100 split is the fastest ever recorded but there was more than just his extreme swimming ability that contributed to this swim. The first thing lead to every team in the race going these blistering fast times was the full body LZR racer suits made by Speedo. Since the 2008 games these suits were banned by Fina for giving an unfair advantage to anyone who was wearing them. The crucial element that gave Lezak the insane time was the way he was able to draft.
In sports such as distance biking or running drafting is used strategically to save energy and move more efficiently. This is done by riding or running right behind the person in front of them. The body in front of them blocks the still air from causing drag on the athletes behind them. This is great for the people behind the leader becuase it saves energy while moving at the same speed. However the leader uses more energy than the riders behind them. While this is used heavily in almost every distance biking and running race it is not possible to go behind a person in lap swimming.
Drafting in the Pool
While this is used heavily in almost every distance biking and running races it is not possible to go behind a person in lap swimming because the athletes are separated by lane lines. However over the years swimmers discovered that when you swim in clean water your body produces a wake similar to that of a boat but on a much smaller scale.
As many people know the wake behind boats can be used to surf on for various water sports. This is the same concept that applies to swimming. However instead of a boat generating the wake, the wave the the lead swimmer is used to propel the lagging swimmer behind more efficiently. This same element of drafting off of another moving bodies wave can be seen in may natural phenomenon such as the V shape that birds ae known for flying in. By staying slightly behind the lead swimmer and staying close to the lane line on the lead swimmers side, you will be slightly more efficient than the lead swimmer. This gives you the opportunity to save energy to push past the lead swimmer at the end of the race.
How Swimmers Prevent Drafting
Since every swimmer produces a wave you would think that it is impossible to prevent other swimmers from drafting without slowing down. This is interestingly incorrect. Just as a boat wave decreases in strength and size as it gets further away from the boat, by increasing the distance between the swimmers the effect of drafting drastically decreases. In the 2016 Olympics Nathan Adrian of the USA stayed on the opposite of the lane than the 2nd fastest team to prevent them from drafting which led to a U.S. gold medal in the 4x100 freestyle relay. In the underwater photo below you can see this in action.