Just watched Boy On a Dolphin (1957) and it has some underwater doublehose action with Sophia Loren (her first feature film) and Alan Ladd. While the story is a bit Τυρώδης the scenery in the Greek Ilses and diving is neat; the equipment even better. This was filmed on the Greek isles of Hydra, Mykonos, Santorini, etc.. back before techno,the Kardasians, instagram and f8kbook ruined the MED for unsoiled travel, diving and sleepy fishing villages. It looks like the underwater stuff was probably shot in a large aquarium tank, I didn't know Calico Bass and Bat Rays are in the MED. And Sophia makes not wearing a wetsuit look 'fashionable' long before Jacqueline Bisset wore a white t-shirt instead of a wetsuit. Look it up at your local library or stream online, I enjoyed it and wish we could go back to diving like it was back then.
https://www.imdb.com/title/tt0050208/