Very nice list of destinations, I thought mine was big!
I am wondering if the impressive marine life in Red Sea has anything to do with what I have heard it is higher salinity than most places?
It could be though I haven't seen anything definitive on this. However I have dove in locations that come close in terms of abundance (such as the Maldives for example) but do not have the higher salinity that you see in the Red Sea...
One of the most striking aspects of diving in the Red Sea is the contrast between the hugely abundant life underwater and what you see when you surface: just desert, sometimes sand dunes right to the water's edge.