Our latest adventure, The Long Walk ambitiously aims to be the longest underwater walk in history, and it presents some very interesting challenges. Water is 800 times more viscous (thicker) than air and therefore, our four Subwalkers are going to use 800 times the energy to move through water! This is part of the reason why a 7.8km walk from Robben Island to the mainland of Cape Town is impossible.
So what are the other challenges? Well, the first and most obvious one is getting air at 15m below the water’s surface. We decided to make our challenge that bit more difficult by being independent from the surface. Using a pressurised hose to pump air from the surface down to divers is a technology that is regularly used in commercial diving; and so we decided it would not be permitted on The Long Walk! Fortunately, a new type of technology called a ‘rebreather’ has been developed over the last few decades that literally recycles the air that you breath by removing the carbon dioxide and injecting new oxygen. Problem solved…kinda! But before I continue with the challenges, let me try to describe what it feels like to walk along the ocean floor. For our first experience of an underwater walk, we travelled to a tiny paradise island called Lembongong, which is a 30 minute ferry ride off Bali. Here they offer you the chance to ‘walk with fish’!
I’ve been fortunate enough to dive in both the Red Sea and the little known archipelagos of Mozambique, and I can honestly say that this experience is one of a kind! The islanders have got a little cheat though, which makes all the difference. They give you a little container of fish food, and when you squeeze it, a rainbow of tropical fish appears around you… It’s mind-blowing!
Back to the science of walking under water, firstly because of the increased viscosity you can’t go fast…at all! So to conserve energy we practiced falling forward underwater, to replicate the action of walking in air, which essentially is a controlled fall! Another peculiarity is having lateral forces working on you. The ocean currents come from all different directions, like wind, one gets pushed around. But unlike wind, water has a much higher momentum (Mass x Velocity2) and the sensations of being pushed around are far more substantial!
The waters of Bali were delicious, like a bath and I could have (and did) spend many hours relaxing in them. The west coast of Cape Town is not as welcoming, and we are expecting a cool 8-10⁰C on the ocean floor. Without heated dry-suits, hypothermia would set in very quickly…hmmm dry suits, more resistance to walking! Okay, so now we are getting to the real challenges, namely CO2, O2 toxicity and decompression sickness which are physiological changes that occur in your body due to being under 2½ atmospheres of pressure for 8 hours. Enter Divers Alert Network (DAN). The best way I can describe DAN is by comparing them NASA. Essentially what NASA is to space explorations, DAN is to underwater advanced technical diving, and remarkably, they have many similarities. The Long Walk Subwalkers are delighted to have DAN on board and will shortly be releasing a detail press release. As an overview: DAN’s South African medical division and international research division team will ensure that the walkers minimise their risk in developing decompression sickness, carbon dioxide toxicity, oxygen toxicity and hypothermia. DAN will employ revolutionary medical equipment including in-water Doppler detection (which detects gas bubbles in the heart), real time blood glucose monitoring, swallowed thermo-pills (for monitoring core body temperature) and monitoring of carbon dioxide levels.