Tomorrow 22 August 2009 the holy month of "Ramadan" is starting for the islamic people. If you travel to an islamic country within the next four weeks it cannot hurt to enquire about the habits of this country during their holy month. We are not talking about religious knowledge. It's more about respecting the inhabitants of this land.
In many touristic places it is permitted to drink, eat and smoke during the day. But in some countries it is strictly prohibited and you could actually run into troubles. You could get a fine or even end up in prison.
Even in countries that are less strict travelleres should show tactful manners. If you leave the beach area there is quite often a village or something similar where locals operate supermarkets for example. They don't like it anyway if tourists are shopping in a bikini. But during Ramadan it is seen as a big disrespect. You also should avoid drinking, eating or smoking in front of the fasting people. In some countries and regions this is not valid for the beach areas. The dive centre or hotel do know for sure about the usual practices of the country you want to visit. Asking doesn't cost anything and misunderstandings can be avoided.
BTW: In Egypt the time was set back to !wintertime! (not kidding) today (21st August 2009 - eg: it's 1pm now instead of 2pm). (jdo)