I don't blame Groupon, nor people looking for the lowest price. Someone trying to find the best price does not mean they have bad intentions, will be poor students, or poor divers. They are just looking for the lowest prices. I always look for the lowest prices - I would be dumb to not do so.
Also, just because Groupon advertises for a scuba school does not mean the scuba school has to "teach" these students all in the same day. They can still have relatively smaller classes.
The blame goes to the scuba school who are being irresponsible and don't understand how Groupon is supposed to work and help a business. Which is, at the very basic level:
1) Groupon makes you set a very low price (to get people)
2) Groupon takes 50% of the cost
3) Company provides the service (which may be at a loss, or a break-even point)
So why would a company be willing to take a loss, or break-even point? It's the same process as a "loss leader" product. Ever been to Staples where they sell a 100-disc spool of CDs at $5 and you think to yourself "but they are losing money"...well now that you are in Staples, they hope they can sell you on their other products where they will NOT lose money.
So, step 4 - the profit - are the students who purchase equipment, come back for additional training, and refer their friends.
The blame resides with the school, not Groupon or the students. In all honesty, the students have no idea and are not being taught properly
I am no marketing genius but it appears that the dive shops taking students to this area should rethink the way they use Groupon.
Would it not make more economic sense to use it to get people to Discover Scuba, Try Scuba or whatever moniker your agency attaches to the process of trying out breathing underwater? If you are doing an entire course through Groupon half of your revenue is lost, thus you pretty much are wasting your time. If you let them Try Diving in a pool for ten bucks (just a number I am tossing out), you give Groupon $5 and you then are only making $5 per person. You now have the chance to SELL them a full price course. Your success may be less but you at least are making a PROFIT (hopefully) on the ones that have agreed to sign up. You now also have the time ( and no pressure from Groupon) to sort out potential divers that need medical clearance to dive or to sell an economical snorkelling session to those that cannot dive. Yes, HONEST sales can be a bit of work but can lead to revenue.
Also, I bet the people diving at Blue Heron are probably not living the "dive dream" , ie fantastic beautiful coral and marine life to see. The few feet of visibility due to poor buoyancy skills will really encourage them to continue!

It seems the fault and resulting problems all stem from a poor use of Social Media, rather than the media itself.