: The water was heavily over-chlorinated to prevent algae growth, causing the crew’s hair to turn white or green and leading to chronic skin and ear infections. Near-Death Incidents and Actor Trauma

To achieve realistic underwater shots without relying on CGI, Cameron converted an in Gaffney, South Carolina, into the world's largest underwater film set.

The shoot was an "endurance test" where the line between acting and genuine terror often blurred. No Cutting Edge But His Own - Journal - Metrograph

: Two giant tanks were filled with over 10 million gallons of water to simulate the lightless ocean depths.

: To mimic the deep-sea abyss, the production floated 20 tons of black plastic beads on the surface and covered the tanks with a massive tarp to block all sunlight.