Everyone has seen or at least heard of the film 47 meters down. Now, it may not be a great film but the plot is at least interesting. The film shows two sisters positioned in a cage that is at 47 meters depth in the water, in this cage they have to take on the ocean’s deadliest predator- the shark. Though the threat of becoming a meal for a shark is terrifying, there are other things that you would have to worry about at 47 meters down such as compression and breathing. So, just how deep are 47 meters and can you survive?
Important plot points
To figure out whether or not you could really survive the events that occur 47 meters down, you should first understand some of the plot points that would in fact be an issue, aside from the shark.
One of the main plot points in the movie is that the two sisters have found themselves trapped, but nobody knows where they are and there seems like there is no hope of them being found. The reality when it comes to snorkeling and diving is that this is a legitimate risk that you are taking. The further that you plunge into the water, the less visible you are to other people. This can be an extreme risk when delving further and further into the water. A way that many snorkelers and divers deal with this is by using different types of divers-down flags. Each flag means different things, but they all mean that there is a diver in the water. This will allow someone who is boating nearby or swimming to stay alert, as if a lot of time passes and nobody resurfaces from the water, an incident may have happened.
Another event that occurs in the film that is one of the bigger plot twists of the entire movie is the introduction of nitrogen narcosis. Nitrogen narcosis is a very real thing and can definitely happen in the real world. This basically occurs when you are breathing in gases at a low depth such as 47 meters and can lead to hallucinations and fainting. Instructors never recommend that you exceed 40 meters as this is when it becomes very common and very deadly.
Though the two sisters use a full face scuba mask within the film and are protected from the pressure that can come with unregulated air, the reality of it is that when you are 47 meters down, you are going to fall victim to the pressure of unregulated air. As you descend into the water, the pressure on your body increases with every meter. In the film, this is shown with the use of a bloody nose. However, the effects would in reality be far more severe than this. If you don’t descend slowly, then the pressure on your body can lead to popped blood vessels, restricted airwaves, and restricted sinuses.
Usually, unless you are diving with a very expensive company, you will use half masks. If you were to descend to 47 meters, you would experience something called mask squeeze. This happens when you are unable to regulate the air in your mask and the mask then squeezes onto your face, which could lead to bruising and other further damage.
Something else that would need to occur when diving to such a depth is equalizing. This is a slow task and it is used when divers or snorkelers descend into the water. This is basically done to handle any harsh pressure in the water, however, there does come a time when the pressure is too much and even equalizing won’t help. When this happens, a number of horrible things could occur as a result. For example, you could burst your eardrums or even have irreversible damage to your blood vessels.
Now that we have covered some of the plot points of the film and some of the events that have happened, it is now time to have a look at the science behind 47 meters down.
How deep Is 47 meters down?
If you find yourself in a position where you are finding it hard to imagine just how deep 47 meters down is, for comparison that is also the exact height of the Statue of Liberty. If you can imagine this in relation to water, that is a substantial depth to explore when diving.
When thinking about just how deep 47 meters is, you should also think about this in relation to the equipment that is required when diving in the water. The most important piece of equipment that could be affected is your oxygen tank.
The further into the water you go, the more air you consume. You can expect to have around about 2 hours of air in a single oxygen tank if you are consuming it at a steady rate above the surface. This becomes far less the deeper down you go, so two hours can quickly become around 30 minutes of oxygen. It is important to remember that when you descend into the water, you need to do it slowly in order to equalize and deal with any overwhelming pressure. It will take you around ten minutes to descend into the water and around 3 minutes to ascend, as you can naturally do this much faster.
This means that you have a very limited amount of time in the water and you don’t have a surplus of extra oxygen to use when you are diving and may be at risk of quickly running out of oxygen when at a low depth. This means that one of your biggest nemesis when diving is your oxygen consumption and this is also why instructors recommend that you never really exceed 40 meters.
It is also important to remember that you shouldn’t ascend all at once. Instead, it should be a slow process that has many stops to help with decompression in order to avoid problems such as the bends.