I just remember something about stolen children all wearing white dresses, theyre being kept under the water in a greek-like place with marble buildings above very still green water. they would be kept underwater doing work with small air gaps under the buildings. every month they would one at a time be given like 10 seconds to go above water to get a fresh gasp of air. very clearly i remember the still green water with a pretty yellow sky. the water is very clear and a child with chains on their ankles swims up for air and then is pulled down when their time is up. it was very cinematic. the ocean or sea of somekind isnt very deep. the sand gets tossed up under their feet when thwy walk. theyre trained to have a higher tolerance of holding their breath since they are babies.