Matt Damon has revealed how Christopher Nolan’s production created the terrifying Scylla sequence in The Odyssey using a mixture of practical stunts and visual effects.

Speaking during a WIRED interview, Damon explained that the cast travelled through a real passage of water aboard the production’s ship.

To create the movement for Charybdis, the enormous whirlpool located opposite Scylla, crew members drove jet skis in tight circles beside the ship. The resulting disturbance created a small practical whirlpool that the visual-effects team could use as a guide.

The production then used an elaborate ratchet system to simulate Scylla attacking the ship.

Stunt coordinator George Cottle rigged six separate ratchets beneath the vessel. During the sequence, the system violently pulled six stunt performers from the deck, representing the six sailors seized by Scylla’s heads.

Damon described the stunt as one of the most incredible things he witnessed during production.

In Homer’s story, Odysseus must guide his crew through a narrow passage between two deadly threats. Charybdis creates a devastating whirlpool on one side, while the six-headed Scylla waits on the other and captures six members of his crew.

Although the creature itself was completed primarily through visual effects, the physical water movement, ship, performers, and stunt reactions were captured practically.

The Odyssey is now playing in theaters.