Mastering the Manu
How a human can create the biggest splash
Manu World Championships in Tāmaki Makaurau: “Mama” Berking winning the world champs with her Manu Jump. Source: Youtube.
Want to beat your friends at creating the biggest splash in the swimming pool?! Try the Manu Jump, a dive bombing method developed in New Zealand. Many innovative dive bomb techniques, including the Manu Jump, are recognized at the biggest big-splash competition, the Z Manu World Champs. The Manu Jump is the most popular form, guaranteed to give the audience a splash.
Step out of the splash zone and get in the water! How does one perform a Manu Jump? First, as you land in the water, you must land butt-first in a “V” shape. Then, immediately upon hitting the water, you must you roll back and kick from a “V” into a straight shape, leaning towards your back. We investigate the fluid dynamics of how this entry and movement work together to form a large splash.
Initial body postures for water entry to perform a Manu Jump. Images from Youtube.
Step by step of how to perform a Manu jump. Images from Youtube.
Though researchers have investigated methods to minimize splash, crucial for the “rip entry” of Olympic diving, researchers had not yet analyzed how to make the largest splash, until now. Like Olympic diving, when analyizing Manu Jumping we must consider water entry and cavity deformation. By analyzing online recordings of Manu Jumping and by using physical models, we determine the best way to make a big splash using the Manu method.
Olympic diving, which minimizes the splash, vs. Manu jumping with a large splash. Olympic Diving source: Youtube.
This project has been featured in New Scientist
Major questions
What is the optimal body shape for water entry?
How can a human affect the water cavity with dynamic movement?
How does cavity deformation influence the size of the splash?
What we’ve discovered
Humans Dive In and Roll Back
From observing human data, we find that a Manu jump is comprised of four distinct stages: water entry in a V-formation, a rollback and kick motion underwater to enlarge the air cavity, the closure and collapse of the air cavity, and the formation of a Worthington splash. This requires aerial maneuvers, such as the transition from a straight to a V-shape, and also an underwater rollback and kick motion.
V-Shape at 45° Angle Creates Deep Cavity and Large Splash
We recorded multiple solid shapes with V angles at 0°, 45°. 90°, 120°, and 180° to find the optimal angle upon water entry that generates the deepest cavity and the highest worthington jet. Not only does the 45° shape create the deepest cavity and highest jet, but 45° also matches the median human body angles recorded for Manu Jumps.
Timely Underwater Body Maneuver Expands the Cavity
We built the Manu-bot to simulate the transition from a V-shape to the rollback and kick underwater. We found that the timing is crucial for generating a large splash: the underwater maneuver must happen after the body enters the water and before the cavity pinches off. This results in an expanded cavity, which collapses and generates a large splash.
From left to right: early, optimal, and late openings.
Large, but Safe Splash: Jumping Parameters for Recreational Water Sports
Humans around the world jump in water— many jump at heights exceeding the recommended 10m limit. In cliff diving, humans attempt increasingly daring stunts. Entering in a V-shape at large heights could be dangerous for divers’ spine. Our study has implications for how future safety recommendations concerning recreational water sports can incorporate different forms of diving.
Read the paper
Mastering the Manu – How humans create large splashes. arXiv (2024).