EXCLUSIVE: Mandy Moore Reveals the Most 'Terrifying' Part of Filming Shark Attack Thriller, '47 Meters Down'

This video is unavailable because we were unable to load a message from our sponsors.

If you are using ad-blocking software, please disable it and reload the page.

In 47 Meters Down, Mandy Moore faces off against 20-foot-long great white sharks. But in this exclusive special feature from the film's home release, the actress reveals the (admittedly, computer generated) predators weren't the scariest aspect of the project for her.

"The most terrifying aspect of this movie, when I initially read the script, was not the sharks," Moore says in the clip. "But the idea of running out of air and being at the bottom of the ocean and trapped, with no way to get up."

WATCH: 'This Is Us' Releases First Scene From Season 2 Premiere -- Watch the Emotional 3-Minute Clip!

Claire Holt, Mandy Moore in '47 Meters Down'
Entertainment Studios

This glimpse behind the scenes of 47 Meters Down also offers insight into how Moore and co-star Claire Holt handled their underwater stunt work. (Which is sure to intensify in the recently announced sequel, which is set to add one more meter of terror. Literally, it is titled 48 Meters Down.)

"There are scenes were Mandy is, like, six meters under, in a mask, having water and blood injected into the mask," director Johannes Roberts explains. "I'm an experienced diver, and I'm not sure I'd do that."

For her part, Moore says of filming underwater, "You want to conserve your energy as much as possible, because when you go for it, ugh...You have to go all out, and then you get to the surface and you're like, 'I feel entirely taxed. I have nothing left to give.'"

If you missed 47 Meters Down, which is available digitally now and arrives on Blu-ray and DVD on Sept. 26, here is the official synopsis:

"Sisters Lisa (Moore) and Kate (Holt) become trapped at the bottom of the ocean when a diving expedition to observe sharks goes horribly wrong. When the cable attaching the cage sinks to the bottom of the ocean, the sisters must figure out a way to get back to safety battling injuries, lack of oxygen, and worst of all, bloodthirsty, great white sharks."

'47 Meters Down' DVD Artwork
Lionsgate Home Entertainment