This tragedy raises all kinds of emotions. It is natural to dwell on the things that went wrong and want to point fingers and find someone to blame. I would like to suggest that a fresh look at possible solutions.
It took me years to figure out why one dive (say at 9:00) would be clear/not clear and the next one (11:00) would be the opposite. When the tide is going out it sucks sands out with it, when coming in it brings clear water (people are just big pieces of sand - LOL). All the dive shops insist on going out on a schedule by the clock instead of by the tide. I will now only dive on an incoming tide. That would be a good regulation for snorkelers. Not only would it be safe it would be a lot prettier.
When I asked my dive shop why they have this rigid schedule their response was 'if we don't take them someone else will.'
One time when we got to Hol Chan there were so many boats I asked that we do Shark & Ray Alley first. We were the only ones there. Then as we came back to Hold Chan ALL the other boats were switching sites. Is there a possibility that a limit be put on the number of boats at any one time?
Are the currents at Shark & Ray Alley as dangerous?
I like the idea that was suggested of colored flags advising conditions.
What other ideas can we come up with?

Harriette
Take only pictures leave only bubbles