Rewatch the Olympic marathon swim to improve your river swimming skills

“This is one of the most fascinating Olympic marathon swims I’ve ever watched,” says Simon Griffiths

Did we just witness the best venue yet for Olympic marathon swimming? Put aside the pre-event worries about water quality and focus instead on the current. This made it one of the most fascinating Olympic marathon swims I’ve ever watched.

The most obvious impact was on the speed of the swimmers on the downstream versus the upstream legs of the rectangular course. Women’s gold medallist Sharon van Rouwendaal swam the first 800m in 6 minutes, which is 45s per 100m. To put this in perspective, in the pool the women’s 100m freestyle world record is 51.71.

Van Rouwendaal’s best 800m freestyle time is 8:24.12 according to World Aquatics. The current therefore boosted her swimming speed by something like 15 to 20s per 100m.

Then, between the first turning buoy and the 1.5km mark, van Rouwendaal took 13:11. Apart from the short section across the river, all 700m of this was against the stream. This was a pace of 1:53 per 100m, something like 50s per 100m slower than she could swim in still water.

A current this strong requires high-level swimming skills to navigate efficiently. We saw swimmers in the middle of the river heading downstream while swimming uncomfortably close to the bank coming upstream. After the first turn, several swimmers were swept almost underneath the Pont de L’Alma as they tried to cross the river. We then saw them swimming diagonally, pointing something like 30 degrees downstream to cross perpendicular to the current.

Instead of turning directly into the current at the second turn buoy, as shown on the course map, they continued crossing the river until they reached the bank before starting the long upstream slog. The strength of the current made swimming even a couple of metres away from the wall much slower. Overtaking here was almost impossible. Swimmers bunched up tight despite repeated whistles from the referees urging them to separate. In later laps, they spread out into single lines.

Such was the advantage of hugging the bank that swimmers covered a greater distance than the straight-line route as they swam around moored boats and other obstacles. Approaching the lap timing check point, which was closer to the centre of the river, swimmers stuck to the bank until the last minute before crossing. Those who tried to cross too soon were punished and held back by the force of water.

The feed station presented the next obstacle. Swimmers had to grab their drinks while being pushed away from the pontoon. If they drifted too far while drinking, they had to scrabble back upstream to get around the next turning buoy, and this cost several swimmers valuable seconds.

The best swimmers used their experience of currents to their advantage. On the final lap, van Rouwendaal jumped ahead of Moesha Johnson under Pont des Invalides, making use of the slower moving water behind and around the bridge pier. Kristof Rasovszky, the men’s winner, repeatedly sprinted out of the feed station, using the current to open up a demoralising gap over his rivals who then had to work extra hard on the upstream section to get back on his feet. Later he said that he and his teammate David Betlehem, who won bronze, spent time practising river swimming in the strong currents of the Danube – it seems that it paid off.

If you didn’t catch the swims live, find a replay. Watch how the swimmers dealt with the current, and how some of those further back lost time when they took the wrong line. Then find a fast flowing river to practise in!