Best dive site in Jeddah is undoubtedly Ms Mary, a site unfortunately located opposite the Naval base hence the coastguard often prevent the dive boats going there, that and the fact that a locally well known dive operator has allegedly been killing the sharks there as well as at the Ann Ann.
I have dived Ms Mary 3 times and seen the resident Silky circling for 30 minutes (some divers have seen 3 there). The reef is named after an undefined wreck, potentially one that lies at about 55m, I have yet to see it, but the deepest wreck I have seen sits at about 45m, beneath the stern of another wreck whose prop lies at about 30m with the bows rising steeply out of the water. I have seen 4 wrecks at the Ms Mary site, there being at least 5 there, but been unable to dive it this year hence am unable to verify the allegations.
DSD also get my thumbs up though some of us more experienced divers need to persuade them to look for new and deeper reefs, they have a list of maybe 30 sites and are very loathe to find new ones.
Other great dive sites in Jeddah would include the Ann Ann, Champagne, Aquarium and Swiss Air, though I completely concur that for truly excellent diving Yenbu the 7 mile reef past point 39 is unbeatable, I'm going there on Friday!
North of Yenbu sites include Um Lujj and Al Wajh with some of the best coral cover on the Red Sea (Dugong!), comparable with Ra's Mohammed, yet there are no dive shops, hotels, companies - nada. You wanna a dive boat then speak to the local fishermen. Awesome.
We are not without our problems in the Kingdom but for virgin reef diving that few have been able to experience, we are spoilt.
If anyone fancies joining me on a trip to Um Lujj in early July, drop me a PM, the more the merrier.