Thanks for the answers, serious and funny ones! Very interesting article on the "dolphin" children.
Yes, I carry a spare mask with me in case mine gets lost. I just wanted to know whether my eyes are normal or not. What 1st Ade says sounds more or less like something I might achieve, so it seems I'm not the only one not to see much at all. As for finding the mask on the bottom, I think I could do it in a swimming pool painted blue, but I'm not so sure about the sea bottom. I hope I won't have the opportunity to find out, though!