Staying at high altitude can cause health problems because the air contains less oxygen. Recognising the symptoms of altitude sickness quickly and responding appropriately can prevent serious complications.
If you are going to go diving the most important rules, which always apply, are: never go out on a new dive without supervision and never go diving alone. Make sure that you always get proper guidance and use good quality equipment. As a rule, you should not fly within 24 hours of scuba diving because a slight reduction of pressure in the aircraft cabin can slightly increase the risk of decompression sickness.