.....although I've only been diving 8 years ( 500+/ 90% ocean) it appears my experiences may have differed from yours.....on my last Bahamas liveaboard trip, for example, the reef above 60 ft. is essentially dead, no fish, algae covered...but below 60 ' the walls were gorgeous...in lots of places global warming has already killed off the shallow reefs...the only healthy reefs left are the deeper ones.....in other places (Cozumel/Bonaire) storms/hurricanes have wiped out all the shallower reefs too...the only thing left intact are the deeper reefs.....so while is is true the light levels/colors are theoretically 'better', in reality that doesn't really matter in many places if there's no life left anyway in the 'shallows'.