Thanks guys ! Somehow, I doubt I ever will be able to swim 200m on the surface (don't know why, may be my buoyancy is not good, but I just can't). But I am very comfortable swimming with a snorkel, mask, and fins, for 300m; I thought that the open water test states that this is enough ?
A friend of mine tried to learn diving, and, according to him, the deeper you are, the more uncomfortable it feels. He managed 30ft, but diving to 60ft ended in an some kind of accident (I'll ask him what exactly happened that discouraged him from scuba diving for life. So I figured out that I'll be happy with 10-15ft, there are plenty of reefs at that depth. Does it make sense ?
I suspect your friends discomfort was psychological in nature. So long as your equalize properly, depth doesn't really have any "feel" to it. Ona truely deep dive, where your bubbles start to sound like bells, you still don't feel the pressure. As for the reefs, I think the best reefs are in the 50-80foot range. The shallow ones get too beat up by storms and such. The deeper ones have more spectacular reef structure, but less fish.