Yep, we were there for a week last March and it's super laid back. You take a plane from Managua to Bluefields that continues on to Big Corn Island. That's kind of a dumpy place with cars, hustlers, etc. Then you take a water taxi/panga out to Little Corn. Takes 45 minutes or so. You get off on the beach just in front of the (only) dive shop.
There are a number of places to stay and you can walk from one end of the island to the other in an hr or so. We stayed at and recommend Casa Iguana which is a 5 minute walk from the beach/dive shop. There are restaurants and such, too, but not much of a night life unless you create it yourself. No cars, noise, smoke, smog, etc. Very peaceful, unspoiled place. I'd definitely go back.
The diving is excellent. Beautiful clear water, corals, lots of nurse sharks and plenty of reef fish. The diving is pretty shallow - max 72 feet and that's scraping your belly on the bottom. One of the featured dives is Grant's Caves (Grant of the Mango Inn, btw who used to own the dive op).
The dive op is wonderfully well run by Miz Elly and Woz: good equipment, well led dives, clean air, nice boat. When we were there, there was only one DM (Davie) and a single boat. Three dives per day that you can take as many of as you like with the occasional night dive (excellent!). All the dives are within 30 minutes of the beach even to the far side of the island.
=Terry
ps. No Spanish Galleon that I know of.
http://www.casaiguana.net/
http://www.divelittlecorn.com/