Nearly all corals that we have in our tanks are collected on one breath or in shallower water... 1-5 meters, or so. Not all, but most. I don't know that you want to go deep enough to where only blue penetrates - if you did James Cameron might want to film it. Most fish from 75-100 feet can fetch $20-100 (rare ones thousands) to a wholesaler whereas most corals bring pennies compared to that.
UV is filtered out by 25-50 meters depending on the type of water and clarity, depending on the source (publications vary)... but that is deeper than most of the corals that we have come from. All of the recreational scuba divers stop at 40 meters where nearly all light is still present in some quantities except for IR. Technical divers at 60 meters still have some red, yellow, green, blue, violet. You have to get below 150 meters before you go strong blue only.