Dr Michelle Dickinson: nanotechnologist on the new research revealing how to improve a manu - The Sunday Session with Francesca Rudkin

Most of the studies that have looked at how humans and animals dive into water have focused on understanding the small splash created by their water entry - think Olympic divers and hunting birds. 

New research published in the journal Interface Focus has not only done the opposite, by studying how to make the biggest splash, but has done so thanks to a fun New Zealand pastime. 

Manu jumping, a sport originated by Māori, involves leaping from bridges, wharves and diving platforms to make giant splashes. 

Each year, this is taken very seriously at the Z Manu World Champs, where the current record is a splash of more than 10m high!

An American fluid dynamitist came across a video of manu jumping on social media and ended up analysing over 50 YouTube videos of Kiwis partaking in the sport to try to understand the science behind creating the largest splash. 

Needing more data than 50 videos, he then built what he called Manubots, which were 3D printed splash-making robots. Each Manubot had a different jumper shape and were dropped into water tanks at different test angles and movements. 

The research found that the best body position for a huge splash is a 45 degree V shape when entering the water. This shape creates a perfect underwater cavity that dramatically collapses and sends water flying - which in physics is a phenomenon known as a Worthington jet. 

The angle of entry is important, but just as important is what the body does after hitting the water. Manu experts are known to do an underwater backbend and leg kick, and this motion was found to keep the air cavity open for longer before it collapses, leading to a bigger splash. 

The V shaped, kicking Manubot confirmed that the perfect splash happens when you open your body just after hitting the water. 

So, if you want to try out for the next manu champs, remember to: 

1 – aim for a 45 degree V-shape when hitting the water 

2 – Jump from the highest height possible that is still safe. 

3 – Time your underwater move so that you open your body immediately after entry. 

While this research might sound ridiculous, the study of how bodies interact with water at high speed is useful in naval design, biomechanics and even injury prevention for divers and athletes.

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