Divers must have a reasonable level of fitness, after all, it is a sport. Several of the courses consist of swims, some timed, of differing distances so it is best to make sure that you are confident swimming in the water without any aid before you apply for the course. A common issue that can prevent people from diving is equalisation problems. As depth increases, so does pressure, meaning that any air spaces within your body must be equalised. You can do this safely by opening the Eustachian tubes, which can be achieved by swallowing and gently squeezing your nose. Equalization issues are a common issue, not matter how experienced a diver you are. Problems can normally be overcome by ascending slightly, attempting to equalize again and slowing your descent whilst continuing to equalize every metre or less. If this does not solve it, do not force it. End the dive and try again the next day.
We all have days where diving is just not for us, so don’t be afraid to tell your buddies you don’t feel fit for diving today, whether physically or mentally. If suffering from a cold, do not attempt to dive as equalisation will be almost impossible. Plus, the ocean isn’t going anywhere. In fact, that’s probably just as important as always remembering to blow bubbles; communicate well with your buddy and the dive team – no one will judge you for backing out of a dive.