47 meters: our heart rate monitor test

In anticipation of the Home Video release of 47 Meters (aka 47 Meters Down), we viewed the film for you by testing its ability to shock the viewer with the help of a heart rate monitor. The shark survival horror directed by Johannes Roberts (The Other Side of the Door) debuted in Italian theaters last May and will be available in DVD and Blu-ray formats from the Oct. 4, 2017 with Universal Pictures Home Entertainment Italia.

As already anticipated, we underwent an experiment consisting of monitoring heart rate changes while watching the movie from home.
Let us point out that this was a "third viewing" for us and that we were therefore already prepared for the various effect, asphyxiating and claustrophobic sequences with which this worthwhile film is replete. The test is therefore, in a sense, offset or at least moderated precisely by the lack of surprise effect.


  • 720p HD led projector for 100-inch diagonal screen
  • Dolby Surround 5.1 + two additional rear channels for a total of 8 speakers (200 watts)

Heart rate monitor

  • Heart Rate Monitor ONrhythm 310 Geonaute: This heart rate monitor consists of a wristwatch and a chest belt (which serves as a sensor and transmitter), both worn while watching 47 Meters. The chest belt measures the potential differences created by the heartbeat and then sends them to the watch with a radio signal.

heart rate monitor

Field trial

It started with a frequency of 67 beats per minute (bpm) and then maintain a stall of 72/76 bpm for much of the film. The increase in heart rates occurred in conjunction with the immersion of the cage in the sea. The peak reached was 90 bpm, a value recorded at the film's highlights (cage rupture, shark attack, running out of oxygen tanks). The heart rate value was restored to 67 bpm in the final sequence.


The protagonists of the story are Kate (Claire Holt) and Lisa (Mandy Moore), two sisters vacationing in Mexico. Unfortunately, the girls become trapped on the ocean floor during a cage dive, 47 meters from the surface. With an hour's supply of oxygen and surrounded by sharks, the two will desperately try to get to safety.

In the cast of 47 Meters (UK - 2017): Claire Holt, Mandy Moore, Matthew Modine, Yani Gellman, Santiago Segura, Chris Johnson and Axel Mansilla.
The screenplay for the film is by Johannes Roberts and Ernest Riera.


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