Staying underwater a key to swimming success

Swimming is one of the big sports at the Olympics and the world’s best will be going for gold.

But here's the tricky part: swimmers don't just race against other people. They also have to swim through the heavy water, which creates a force called “drag” that slows them down.

If the water slows them down so much, you might think the best way to swim fast is to stay on top of the water. But that's not always true!

Swimmers push water in front of themselves, creating waves. Waves are also seen at their feet. Credit: vecteezy.com

Water can be a real drag

When swimmers push through the water, they make waves. And making waves uses up energy, which can slow them down.

 So, what's the secret trick? Staying underwater as long as they can!

Waves aren’t created when we swim underwater, but it’s still important to maintain a good body position (hydrodynamic body position). Credit: jayhem, Antibes, France.

It turns out that it’s much faster to swim under the water so that waves aren’t made – at least during starts after diving into the water and during turns after pushing off the wall when swimming speed is the fastest.

And since drag is greatest when swim speed is fastest, it’s most important to do it in the sprint events. Of course, it’s hard to do it in the longer events (say, 400 metres and further) because swimmers need to breathe more, and swimming underwater becomes more difficult.

The effect of swimming underwater was known long ago. In the 1956 Olympics in Melbourne, a swimmer named Masaru Furukawa from Japan swam most of his race underwater. He won, but they had to change the rules after that because it the swimmers did most of the race underwater instead of swimming on top of it!

These days, swimmers have to come up for air before they reach the 15-metre mark in each lap. You can see this mark where flags are hanging over the pool.

Swimming underwater is seriously fast…watch the swimmer in Lane 1 (nearest lane), who chooses to stay underwater. Of course, he was disqualified for breaking the rules, but it’s great fun to watch!

How to swim underwater

To make the most of being underwater, swimmers use a cool move called the "dolphin kick." They move their body like a wave, just like dolphins do! This helps them swim super fast underwater.

When you watch the races, pay attention to what happens right after the swimmers dive in and when they push off the wall after a turn.

If you look closely, you might see:

1. Who stays underwater the longest (at least to 15 metres)

2. Who kicks their legs the fastest

3. Who swims deepest under the water before coming back to the surface

4. Who moves their feet (not their whole legs) up and down the most, like a dolphin's tail

Here’s a great video (below) to show a good technique and how good coaches and scientists can help swimmers to improve their dolphin kick:

These underwater tricks could help a swimmer win by just a tiny bit - but in the Olympics, a tiny bit can mean the difference between winning and losing!

So, when you're cheering for your favourite swimmer, remember to watch what's happening underwater too.

 Do they stay deep underwater as long as they’re allowed to? Do they use a fast dolphin kick?

The underwater phase of the race is as important as the race on top of it.

The swimmers who are best at using these underwater tricks might be the ones who win the gold medals!