A while ago I had a friend who was a marketing major at a local college. She needed a project so we decided to to a business analysis of dive shops in the SF bay area. Note this only covered the bay area proper not Monterey, which as a resort, is a special case...
Our conclusion was that, on a per customer basis, that there are 2 or 3 times the number of stores per customer as other sporting goods stores in the sf bay area. This was based on population, number of divers, expected sales etc.
Given this (and assuming that rent and other expenses were similar) the stores needed to make much more money per customer than other sporting goods stores in order to stay in business. Or there only needed to be about 1/2 as many dive stores as there are to support the customer base.
There are three way that an industry can survive this, 1) drive up sales, make the gear fashionable and generate a preceived need to trade gear often, running up sales 2) fat margins 3) or profitable auxiliary sales (not training as it, as a lose leader, is what brings in new customers and their gear purchases. Otherwise expect consolidation.
One particular store, which we examined in depth, had very high fixed expenses. Rent was not two high, but the staffing coast were through the roof (6 full time employees, three with families) given that I never saw two customers in the store at one time, and saw no customers at all on many visits. Their level of knowledge was not that high, and they sent out all or most of their repair work.
Since that time three stores have close, to not reopen. In my mind this is a good thing. I would rather have a small number of good local dive stores (I do know of three, which I patronize when I think its appropriate) than the current crop of good/bad stores. Unfortunately i fear that the best stores will close and leave the cr**py ones