Large basin on soundstage or backlot for water, submersion, underwater sequences — temperature control, lighting rigs, underwater camera mounts standard.
A water tank is the infrastructure solution for anything that takes place under or in water. Whether diving scenes, underwater shots, swimming sequences, or flood effects — nothing runs professionally without a tank. Most major studios have at least one permanent tank on their premises, often several in different sizes and depths. Some are 20 × 12 meters and 4 to 5 meters deep — massive enough for real underwater camera movements and actor maneuvers.
Practicalities on Set: The tank requires constant preparation. Water changes, temperature control (usually 26–28°C for longer shoots), chlorine and pH level management — otherwise, you risk skin and respiratory irritation for the performers and divers. Lighting is critical: water brutally absorbs color and light. Cold water HMIs, special underwater lights, and often reflectors around the tank are standard. The light must penetrate the water surface and sometimes several meters of depth without distorting refraction effects or blinding the camera.
Camera rigs for underwater shots are expensive and specialized. ROV (Remote Operated Vehicle) systems with HD or even 4K cameras, Steadicam underwater rigs, or free divers with handheld cameras — each approach has its limitations and costs. The camera itself must be in a pressure-resistant housing, with special optics due to the refractive index differences between water and air. Focusing underwater is an art — your depth of field is minimal, and focus pullers must work precisely.
Safety is not optional. Dive masters, lifeguards, on-site medical equipment — all involved must be certified. Actors need breathing air, often through rebreather systems, so you don't have to reset every five seconds. Pool accidents happen lightning-fast and are severe. Therefore: clear communication, secured lines, buddy system, always a first aid team directly at the tank. The 10-hour shoot becomes a 14-hour marathon because each underwater take has to be set up three or four times.
Small tanks for close-ups or aquarium effects are also useful — sometimes a 2 × 2 meter pool is enough for close-ups or partial shots. But for real freedom of movement and actor safety: a large, stable, well-equipped tank is an investment that pays off for high-quality underwater material.