... and is already considered the most momentous dive movie ever made?

The Avatar saga will evolve into five chapters and is James Cameron’s personal story with the distinctive message to not sacrifice everything for pure greed and conquest. It might take all five movies to really make that message loud and clear for the whole world. James Cameron is a free- and scuba diving explorer at heart and he wants to share his inspiring vision of the underwater world in Avatar II. The movie is said to last about three hours and currently only the following is known about the plot: 12 years after exploring Pandora and joining the Na'vi, Jake Sully has formed a family with Neytiri as they are wandering across the expansive world of Pandora, meeting new allies in the form of the water-dwelling Metkayina clan led by Tonowari. Everything changes when the R.D.A. (Resources Development Administration) once again invade Pandora to finish what they’ve started.

Many of the actors doing a lot of underwater work themselves, a substantial part of that involves freediving, which many of the crew including stars Kate Winslet and Sigourney Weaver had been trained in by Kirk Krack, a world-renowned expert in freediving. The cast, among a seven-year-old child, are up to four minute breath-holds. He himself spent two years working on the film as a freedive safety, training and educational consultant. Most other movies with underwater scenes are using the “dry-for-wet” method, where the scenes are shot in the dry and the water is only simulated by technical manipulation, quite to the contrary of Avatar II where all scenes are “wet-for-wet” shots, hence real performance capture underwater. It is said that the crew logged over 200’000 freedives between the cast, safety, camera people, grips, special effects technicians. On principal cast days some crew members spent about 12 hours in the water tank. Apparently, two of them logged 3 ½ hours of breath-holding on one busy day.

Even though the principal photography has been wrapped by the end of 2019, the movie will not be released until 17th December 2021, due to the extremely complex post production.

That gives you plenty of time to dive into the magical, somewhat AVATAR-like cenotes of the Yucatán peninsula in Mexico.

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Sadly not anymore. Although all life originated from water, we've gradually lost many of our biological ties with it. But there is still one astounding evolutionary adaptation slumbering in all of us: The mammalian diving response or dive reflex We share it with whales, dolphins, seals, penguins and the likes. While they need it to function in their everyday life, it is designed as a survival mechanism to us. However, we do not benefit from its effects merely in an emergency, but as well when diving on breath hold = freediving a.k.a. apnea.

Initial stimulus

Facial immersion in water or even just facial contact with water; the colder, the faster the reaction. The receptors in the face, especially on the forehead and around the nose, are connected to the trigeminal nerve. Said nerve transmits the information to the brain, which stimulates the vagus nerve. This results in the immediate closure of the airway as well as a number of physiological changes to optimize the body’s oxygen management towards conservation.

Additional stimuli: Breath hold, pressure increase Responses 1. Laryngospasm - only in infants up to 6 months: The vocal cords are immediately closing, thereby constricting the windpipe and thus inhibiting water from entering the lungs => prevent drowning. 2. Bradycardia - slowing of heart: The heart is one of the strongest muscles in our body and every heartbeat consumes oxygen. During breath hold our body will naturally slow down the heartbeat by 10-30% (in trained freedivers up to 50%+) to conserve oxygen and consequently extend our time under water. 3. Vasoconstriction - constriction of blood vessels: When our blood vessels constrict, blood flow to our extremities is reduced, thus increasing the concentration of oxygen-rich blood towards our vital organs (lungs, heart and brain). 4. Blood Shift - As a result of the vasoconstriction, blood is shifting from the extremities into the vital organs and chest cavity. The alveoli and capillaries in our lungs become engorged with oxygen-rich blood (= incompressible), which replaces the air space (= compressible) in our lungs. The blood acts as a cushion, preventing our lungs from collapsing when dving deeper than our residual lung volume (~35m+). Blood shift also occurs in the other organs of the body in a similar manner and with the same result. 5. Spleen Contraction - The spleen, an organ that stores red blood cells, contracts up to 20%, thereby releasing red blood cells into our circulatory system. This means that more oxygen can be stored in our blood. Furthermore, the additional blood cells allow the body to resume its normal balance faster after a prolonged breath hold. Life Hack

Calm down your nerves at any time by enabling the mammalian diving response. Simply put a cold wet towel on your face; make sure to cover the forehead and the nose. Because the dive reflex excites the vagus nerve, your heart rate drops and your body starts relaxing. To reinforce relaxation, breathe slowly and deeply in a ratio of 1:2, e.g. inhale for 10sec, exhale for 20sec, if you like you can also add a short pause (= breath hold) after the inhalation.

New data suggests that our evolutionary cousins the Neanderthals were diving in the ocean for clams.

It adds to mounting evidence that the old picture of these ancient people as brutish and unimaginative is wrong. Until now, there had been little clear evidence that Neanderthals were swimmers or even divers. But a team of researchers who analysed shells from a cave in Italy said that some must have been gathered from the seafloor by Neanderthals. The Neanderthals living at Grotta dei Moscerini in the Latium region around 90,000 years ago were shaping the clam shells into sharp tools. Paolo Villa, from the University of Colorado, Boulder, and colleagues, analysed 171 such tools, which all came from a local species of mollusc called the smooth clam (Callista chione). The tools were excavated by archaeologists at the end of the 1940s. The beached specimens were opaque, sanded down through being knocked against pebbles on the shore, perforated by other marine organisms and encrusted with barnacles. Most of the specimens at Grotta dei Moscerini fit the criteria of shells that were collected on a beach. But one quarter of them had a shiny smooth exterior, showing no signs of such wear and tear. This suggested they were collected from the seafloor while the clams were alive. "It's quite possible that the Neanderthals were collecting shells as far down as four metres," said Paola Villa. The evidence is in stark contrast to our old view of the Neanderthals spending much of their time chasing or scavenging big game animals. It's known that Neanderthals gathered mussels from estuaries and fished in shallow waters, but there has been little clear evidence for physical aquatic activities. "It's more evidence to place Neanderthals into these coastal environments and at points in time making use of coastal resources, not just for food, but also as a raw material for tools," said Dr Pope. He said that decades ago, this type of resource-gathering had been used to distinguish early examples of our own species, Homo sapiens, from the Neanderthals. "We can't find that distinction anymore," he said.

Imprint: This blog post contains extracts of a BBC Science & Environment article.

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