THIS!!! This statement is critical to the facts in the lawsuit. Sotis was not Stewart's instructor on the fateful dive, he was a safety diver (one of 3 IIRC) who had a different duty of care in a very legal sense.
I am (have been) a safety diver on a number of film shoots. The Diving Safety Officer along with the Safety Divers, as a general rule, have absolute control of the shoot, with the cooperation of the producer and studio. And the studio's insurance company. I no longer carry instructor insurance, I carry a commercial policy for that type of work, and a hefty rider for each shoot. Sometimes for every day of the shoot, depending on what talent is in the water. Now, I've only worked on commercials and documentaries, never on a feature film like Pirates of the Caribbean. Which was shot in a tank in Mexico, because it was far more easily controlled than in the ocean. When the safety diver says "I'll go retrieve the anchor, you stay on the boat", the talent stays on the boat. But the safety diver would never ever ever go retrieve the anchor. That's the job of the vessel crew.