I just completed my first 4 dives for my open water certification. I am of very good health and condition. Is fatigue a possible side effect of beginning diving? I am very tired today and completed my dives yesterday.
First, if you did 4 dives in one day for your SCUBA certification, it was a violation of your agency's standards and it's no surprise that you're tired. That's a lot of diving, especially when you're new. If you only did two dives and are tired, there are things you can look into.
You should be able to improve how you feel by making sure that you control your ascent rate during the dive, and ascend very slowly for the last 30', and especially for the last 15'. Taking a whole minute to get from 15' to the surface wouldn't be too slow.
Staying well-hydrated also helps, as does proper weighting and trim, and being relaxed while you dive.
Many people feel that Nitrox also helps a lot, although I'd recommend waiting until you're certain about your buoyancy control before switching to Nitrox, since diving with it requires that to don't exceed the maximum depth for the mix you're breathing.
In any case, you're not alone. When I first started diving, I actually had to pull off the road on the way home because I was falling asleep in the car.
Terry