A 73-year-old scuba diver lost her leg to a shark. Now she’s back in the water
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TheGuardian
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Tuesday, 9 April - 11:00
Heidi Ernst took up the sport 13 years ago. After 523 dives, disaster struck. But a prosthetic leg – and a sense of humor – has kept her swimming
Shark tattoos adorn each of Heidi Ernst’s calves. You can see them now as she sits at an Iowa clinic, gazing out the window. Around her neck are two silver necklaces: one clasps two dolphins, the other a shark. Her blue eyes twinkle like the ocean. The lines on her face reflect not her 74 years, but the fears she has faced.
“I’m so excited I can hardly talk,” she says to her neighbor, who drove her to this critical medical appointment in mid-September.
Brown researchers set up a belly flop-like water experiment using a blunt cylinder, adding an important vibrating twist to it that ultimately led them to counterintuitive findings. Credit: John Antolik and Daniel Harris.
We've all had the misfortune of botching a dive into the pool and ending up in a painful belly flop—or perhaps we've done it deliberately to show off and instantly regretted that decision. Hitting the water in that body position can feel like hitting concrete and lead to bruising or (if one is falling from a greater height) internal injuries. While the basic physics is well-understood, scientists are always looking for greater insight into the phenomenon in hopes of finding novel ways to ameliorate the impact.
Scientists at Brown University have found that, surprisingly, adding a bit of extra spring to a body hitting the water can actually increase the impact force instead of decrease it under certain conditions, according to a
new paper
published in the Journal of Fluid Mechanics. The implications go beyond protecting divers; a better understanding of the hydrodynamics will improve designs of naval ships, seaplanes, or projectiles, as well as underwater autonomous vehicles.
From a physics standpoint, we're talking about an elastic body hitting the surface of water. The stress of moving from the medium of air to the much denser medium of water exerts a huge force as that body displaces it. The cohesive forces between water molecules are stronger at the surface, making it harder to break through. (It's why diving competitions often use aerators to create bubbles in the water, breaking the surface tension to protect the divers.) A large volume of fluid must be accelerated (displaced) in a short timeframe to match the speed of the impinging body. The larger the surface area of the object hitting the water, the more resistance there will be—and with belly flops there will be a much larger surface area than with a simple swan dive, resulting in that signature slam.
An Apple Watch showing dive metrics. [credit:
Apple
]
In September, Apple announced a new wearable called the
Apple Watch Ultra
, and one of the company's key pitches for the device was its use as a diving computer. Now Oceanic+, the app that makes that feature possible, launched exclusively for the Ultra, Apple announced today.
The Watch Ultra has depth gauge and water temperature sensors that drive some of the features in the app. To access a few of those features—such as decompression tracking—you'll have to subscribe to the app's premium version for $4.99 per day, $9.99 per month, or $79.99 per year. There's also a family plan at $129.99 annually. If you don't subscribe, you can still use some key features like dive logs, depth tracking, and so on.
The app—which was developed in partnership with Apple by a company called Huish Outdoors, lets you track dive conditions like tides, water temperature, and more. Here's a quick summary from Apple's
blog post announcement
:
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