"The bright, vibrant colours you see in pictures aren't what you will ever see underwater on a tourist trip.
Red light, and the colour tones nearest red, are basically gone after 1 meter of seawater. There's simply not enough light in that spectrum making it from the surface, to the coral, to your eyes. That's why a lot of fish are red - the colour basically vanishes unless it's up in your face."
Nonsense, I do a lot of underwater photography and this simply isn't true. Our eyes are incredibly good at adjusting to the reduction in the colours as we go deeper, and it's only really when you start going below around 20metres that you really start to get so little light that your eyes just can't compensate well anymore. Reefs are incredibly colourful down to the common basic recreational limit of 18m - something like a rainbow parrotfish will look exactly as colourful as it does in any of the most colourful pictures you can find on Google images at 15 metres.
There are of course times this isn't true, when there are issues with water conditions such as diving in water that is suffering some form of algae bloom, or silt kick up where the algae or silt particulate in the water will of course have light bounced of of itself.
"The other thing the photographers do is they take photos with the strongest possible flash, and only take photos in the coolest parts of the reef; nearest the cool open water and on a slope, not on the hot flat deck that's right below the surface and catches the refracted sunlight 10 hours a day with the least mass flow."
Again, nonsense. We take photos wherever we can find a great photo and that's never restricted by depth or geography, but simply whether we're in the right place at the right time to get a great subject. That can be at 30cm, or it can be at 100 metres. My camera has perfectly good enough white balance to shoot consistently without my strobes down to about 10 metres. Below that I do indeed take strobes, but I've had some great shots without them even at 18m.
"Other things to consider are that you're less likely to see Nemo and more likely to find small hussars, sea cucumbers, and the stingrays and reef sharks."
That really depends where you go, many tourist dives are actually unlikely to see things like reef sharks and stingrays because animals tend to get bigger the deeper the water and they tend to keep tourists who aren't that comfortable with diving in relatively shallow (i.e. above 18m) dives. In some regions you of course get these creatures coming into the shallows, but for the most part on a tourist dive you're going to stay fairly close to the coast, and you'll see countless smaller fish like you would typically see in the most colourful marine aquariums.
It's fairly obvious you've never been diving, because you're basically wrong about everything. The GP was referring to the fact that in some areas the damage to reefs is substantial such that the beautiful colours are gone, not that reefs that are healthy are not colourful below 1 metre.