2 scuba divers descending - how deep is 47 meters?
Descending into the unknown. How deep is 47 meters and could you survive that depth? Photo by Jacob Waldrop / Unsplash

Scuba divers have polarising views of the fantasy movie, ‘47 Meters Down.’ It’s great because there just aren’t enough scuba diving films out there, but at the same time it paints scuba diving and sharks in a pretty scary and unflattering light. Either way, it is highly entertaining and fun to watch. So let’s take a look at exactly how deep is 47 meters, and what would happen if we were scuba diving at that depth!

How Deep is 47 Meters?

47 meters is definitely a deep dive. It is:

  • Slightly over the height of five average American football goals stacked on top of each other
  • 2.5 times the height of a Boeing 747
  • The height of the Statue of Liberty from the base to the torch

How Long is 47 Meters?

If you want to know how long 47 meters is, then you could compare it to:

  • Half the size of an American football field
  • Half the size of an average European football field
  • 2 Tennis court lengths

How Far is 47 Meters in Feet?

47 meters is the equivalent of 154.2 feet.

A meter is a standard metric unit that is used to measure length. The metric system is widely used around the world, with the exception of three countries; the United States, Myanmar (formerly known as Burma), and Liberia. These countries uses the imperial system which includes feet.

How many miles is 47 Meters?

47 meters is 0.029 miles.

A mile is an older unit of measurement that originated from the Roman mille passus, or a “thousand paces,” which measured 5,000 Roman feet. In modern times, a mile is now 5280 feet, which is the equivalent of 1.609 kilometers.

How many yards is 47 meters?

47 meters is 51.39 yards.

In ancient times, the easiest way to measure things was by using your body which is where the measurement terms, ‘thumb, hand, foot’ comes from. Apparently, in the 12th century, King Henry I of England fixed the yard as the distance from his nose to the thumb of his outstretched arm. Today it is 36 inches or 3 feet.

Is 47 Meters Down based on a true story?

Now that we can imagine the length and depth of 47 meters, it is time to ask whether the film was based on a true story, and what would happen if you were scuba diving at that depth.

Firstly, 47 Meters Down is not based on a true story. Johannes Roberts, the writer and the director of the film and its sequel, 47 Meters Down: Uncaged, had this to say in an interview.

“For me what works about both movies is that they’re actually, as preposterous as they are, you know, they’re movies.”

“But you know, if you went down 47 meters in a cage to the bottom of the ocean, with a tank, and you were an inexperienced diver, you would probably last about three minutes before you died or ran out of air.”

“So yeah, sure, it is ridiculous…these kind of things. But it is a movie, you know?”

So there you have it, one of the writers and director of the movie has said that 47 Meters Down is just a movie. He also acknowledges the scuba diving inaccuracies involved, but let’s try imagining the scenario when diving at 47 meters down.

How long does a scuba tank last at 47 meters?

Depth

Surface

10m

20m

30m

40m

Pressure

1 bar

2 bar

3 bar

4 bar

5 bar

Volume

1

1/2

1/3

1/4

1/5

Density

1x

2x

3x

4x

5x

According to Boyle’s Law we will be at 5.7 bar of pressure at 47 meters. To find out how long a scuba tank lasts we would apply this law at 47 meters. This means the density of the gas is 5.7 times than that at the surface and we will be using the gas 5.7 times faster.

So if it took you 1 hour (60 minutes) to breathe and use up the scuba tank on the surface at 1 bar, then you will be using it 5.7 times faster at 47 meters. Therefore; 60 minutes / 5.7 = 10.52 minutes

If you took you 2 hour (120 minutes) to breathe and use up the scuba tank on the surface at 1 bar, then it would be; 120 minutes / 5.7 = 21.05 minutes

Regardless of how well you can extend your breath (and remember, you must never ever hold your breath), a scuba tank at 47 meters will not last very long. This is excluding the amount of time and the air you will use to descend and of course, slowly ascend.

How long would it take to swim up 47 meters?

It is very important to ascend and go up slowly while scuba diving. There have been many tests to figure out the safe ascent rate to avoid decompression sickness. The U.S. Navy and the National Oceanic and Atmospheric Administration (NOAA) uses a rate of 30 feet or 9 meters per minute, while recreational diving agencies can differ from 30-60 feet (9-18 meters) a minute.

So if you were using PADI’s suggested ascent rate of 18 meters per minute, then it should take you 2.6 minutes, at the quickest, to swim up from a depth of 47 meters. This is considered an older model for ascent rates.

Most dive computers will now be set to an ascent rate of 9 meters per minute, which would take 5.2 minutes to ascend. This is not even taking account of the need for Decompression Stops and a Safety Stop.

Read More: What Should Divers Do For Their Own Safety?

47 Meters Down Nitrogen Narcosis

The movie 47 Meters Down (spoiler alert!) ends with Mandy Moore’s character, Lisa, hallucinating that she has successfully rescued herself and her sister. This hallucination is explained by nitrogen narcosis which is caused when diving and breathing gases at a deeper depth.

The Easy Explanation: Nitrogen Narcosis

Nitrogen or gas narcosis can happen at 47 meters down. It is actually quite common at depths beyond 30 meters, and can be more severe at greater depths. This is why most diving agencies will have a recommend recreational depth limit of 40 meters.

Comment below to let us know what you think of this movie and check out our interview with Bolívar Sánchez, the Marine and Diving Coordinator from 47 Meters Down and 47 Meters Down: Uncaged.

Emma was terrified of the ocean but dove into her Open Water 7 years ago and hasn't looked back since! She worked as an underwater videographer for several years and is now a PADI Master Scuba Diver Trainer. She currently runs a dive shop on the island of Koh Tao in Thailand and is the founder of Down To Scuba.

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