My boyfriend and I are beginner divers and are looking to go somewhere for a week in the beginning of August to get certified. Where is the best place to dive during this time? Is Egypt any good? We are quite flexible on where to go but just want to be where the water and sites are good and visible (with no rain).

Well you certainly won't get any rain during August in Egypt. If you do decide to go to Egypt, go to Dahab. Nice laid back town, cheaper than Sharm, lots of dive sites to choose from with easy shore entrances.

Agree with the previous post, no chance at all that you'll get any rain in Egypt! I've no direct experience with Dahab, but have been in both Sharm and Marsa Alam and for the diving they are equally good but completely different places. In Marsa Alam you'll have no other choise than staying in a hotel placed in the middle of the desert (absolutly nowhere to go!) while sharm - especially in august - is as busy as it can be, mainly with noisy italian and rude russian package turists. Consider that sharm's dive sites in august gets equally busy, and on the most famous dive sites the boats queu up like traffic jam at rush hours and you will very likely see more divers than fish. If you decide to go, just make sure you pick the right dive center, some are really excellent, some are directly criminal. And make sure you bring plenty of tummy problem remedials to Egypt...

Agree with the above post re dive centres. There are loads to choose from, with hugely varying practices and safety records. Be sure to post when you decide a destination and ask for recommendations.
You will get loads of package tourists in Sharm, and personally I think Sharm lacks a lot of personality. Dahab never really gets so busy (well not in the last two years I lived there) and there are no boat trips to access dive sites. Diving is much cheaper in Dahab than Sharm, and some dive sites, such as the Thistlegorm, are cheaper to do as a trip from Dahab, than they are to do from Sharm!