Interesting. I also recall seeing "dive safari" used to refer to a land-based trip in which the guide will take you diving in multiple places along a multi-day route. We did our own in Bali, hiring a different guide in each place along the coast, but I saw advertisements for dive safaris in which the guide would have stayed with us for all or part of it. I kind of like the idea, if it fits the region. (Food and accommodations are often cheap, plentiful and excellent in Asia.) But to echo what you already pointed out to the OP, I would not think the safari format would fit Egypt, as the best dive sites are far from the coast, and apart from scattered resorts/hotels there are few amenities along the coast to cater to the needs of overnight foreign visitors--even assuming they have a dock that could accommodate the vessel-- which in sum is why liveaboards are so common there.