If you are a diver and have a card or log book, take it with you. I forgot mine once when I was visiting Key West for less than a day. The diving equipment rental company wouldn’t believe I had one and instead insisted that I take a diving test in the local swimming pool before taking me out on the boat, and I just didn’t have enough time.
Note that there are many different bodies around the world which award diving qualifications (e.g. PADI, BSAC etc.) so you may need to know the equivalent qualifications for each to know which level you are at (for example, Sports Diver, Instructor, etc.), especially if you want to do more training, so find out before you go. There are plenty of places online which give this information, for example, here.
