[hellosailor]

I suspect the logic is "Divers often have boats. Divers go to a store for air, sometimes every week. Gee...if we serviced divers, we could get more boat owners to stop by West every week, and then they might buy stuff for their boats while they were here."

The logic might work, depending on the cost of adding dive services to a store.

"Leave scuba to shops that have expertise and training and well kept equipment. " Oh, right, like there are any of those on this planet? Come up to the northeast, plenty of gen-you-whine certified shops give short fills, dirty fills, outright lie about VIPs being necessary, outright lie about plus hydro....

You get better odds on the local indy gas station having a clean restroom. Sad to say.

 

[hellosailor]

"but they didn't do more advanced stuff like hydrotesting"
AFAIK no SCUBA shops do hydro testing. You need equipment and a trained operator, so they always job it out to the local extinguisher companies, who do enough volume to justify the equipment.
The only real question is how much to mark it up and how fast to turn it around. In the northeast, the SCUBA shops also all play dumb and claim you need a VIP with the hydro. Wrong, DOT regulations require the hydro shop to actually perform the VIP before any hydro testing is done. Less chance of it blowing up in their faces that way.
The Three Stooges once did a piece about a law firm named "Dewey, Cheetham, and Howe". West could easily do better than the average hungry small owned SCUBA shop.

 

[hellosailor]

"West Marine will fill your tank with air imported from China... "
Is that like Chinese food? You know, you want more just an hour after you've had it?

WM and even WalMart already do sell "scuba" gear. USDivers masks, fins, snorkels, maybe Mares and Scubapro as well. Not a full line and not the high-end stuff to be sure, but once the brand is in the door....

And Walmart has openly said they want to challenge Amazon at being a logistics system for all kinds of retailers. Go to WalMart's web site and they're offering goods from thousands of other vendors, delivered to your home or your local store--in case you can't be home all day waiting for packages.