@Willeke I have some claustrophobia too, mostly on a crowded airplane. I thought I would be claustrophobic diving, but the first time I felt that way, I said to myself: "You are breathing, aren't you?", and I took longer, slower breaths and I was OK. Also, I knew all I had to do was tap the instructor and point upwards we would go to the surface. After that first mild attack, I have been OK, but I don't think I would ever be able to dive in underwater passages or inside a shipwreck.