Placencia in south Belize is a lot smaller so maybe more of what you want. The north part is a little more developed though - some beachfront resorts etc. The barrier reef there is a long boat ride out (hour?) though so typically 2 dives/day is about it. Nice shallow beach so no shore diving - at all. One draw there during full-moon weeks in spring is the Cubera Snapper spawn - that brings in the Whale Sharks. At Gladden Spit you can dive with them. Check Splash Dive's website - they list dates. Friends dove there a couple years ago - on two trips they dove with 8.
Also it's one area from which you can access a lot of the Belize eco stuff on day trips - Mayan Ruins, Cockscomb nature preserve, howler monkeys, cave tubing etc. Even more off the beaten path is Caye Caulker. Only two dive ops there - all I know about it.
we love of the beaten path resorts
In Cozumel? You're kidding right?
Near Cabo Pulmo is a site called El Bajo. Pretty interesting boat dive....
http://www.cortezclub.com/diving/diveelbajo.shtml
This is one of the premier dive sites in the world for schooling Hammerhead sharks. Schools range from between six to hundreds travelling in a clockwise direction around the seamount for unknown reasons. While schooling, hammerheads are not aggressive, and reassuringly enough they actually appear disinterested in divers. As a seamount El Bajo is home to an abundance of sea life, mass schooling fish (amber jacks, tuna etc), octopus and the impressive Panamic Green moray; a colony of over fifty can be found in a small canyon. Aside from possible encounters with hammerheads frequent visitors to the seamount include; whale sharks and giant pacific manta rays. NOTE: this is an Advanced Open Water Dive.
Check into Dominica also. I don't know much about it except it's hard to get to. So that may have kept it less commercialized. I've always seen it listed as good diving location.
Saba would be off the beaten path. Only one small hotel, some guesthouses and few restaurants. No cruise traffic and no beaches - the whole island drops off into the water. Hiking is the other activity. Short flight/ferry ride from St. Maarten. My latest often-reposted video - not my work:
[youtubehq]Wdzv96WkYyI[/youtubehq]
---------- Post added July 30th, 2014 at 12:11 PM ----------
Or West Curacao - it's dead quiet out there. And really excellent shore diving - Playa Kalki is one of the best on either island IMO. Lodge Kura Hulanda is the upscale place, All West Apt's. nearby is the divers place. 4-5 restaurants or a 45min. drive to town or the airport.
I'd personally rate Curacao diving better than Roatan. There's certainly more diversity - it's also a known macro photo location yet there's some other interesting things - wrecks, the Mushroom Forest etc. Downtown is pretty touristy though - the Mega cruise port is 2 blocks away. Nice when they're gone at night.