For her work, Morrison hires assistants who know cameras and lights, but who are also strong swimmers and, often, scuba-certified. Her preplanning stages include sourcing oil-based makeup, and water-testing wardrobe and props. They should be water-friendly and not too heavy or buoyant. “If a prop is glued together, it will fall apart in the water,” Morrison warns. Water temperature is important, too. Her pool is heated to 90 degrees, which can also cause a prop to disintegrate or warp.