Deserted Places & Uninhabited Islands:
The Carter's Cays group western cays such as Joe's and Jacks* I often (but not always) find a bay to myself at Umbrella* Bay on ocean side of Allan's-Pensacol*,, occasionally at Powell, sometimes the northern bays of Manjack as well as off No Name. Spoil Cay tends to get visitors during the day, but I've often had to myself at night. Further south, Water
Cay and Deep Sea/Snake Cays are good bets.
Ruins and Abandoned places:
A few small ones on Great Sale
, more on Carter's Cays both associated with the former missile tracking bases.
Places with few people
New Plymouth is my favorite Abaco
town. Marsh Harbour is good for reprovisioning. Cooper's town and Fox town* are smaller, less visited communities. As mentioned above, there are many uninhabited islands. Manjack has good trail walking and a very long ocean side beach.
Great snorkel spots:
Almost any part of the barrier reef on a calm day. It's very close at Great Guana. You can swim from the tip of the island out to the reef there. Fowl Cays is a reasonable inside reef as the is the one by Sandy Cay which can get some swell.
Lobstering in season.
* North of normal chartering grounds.
When chartering, I always sign the waiver to go north of New Plymouth so we can enjoy Manjack and Powell. I've done a few 10 day charters in the Abacos where we've had an anchorage to ourself 8 of the 9 nights out. On my last charter
we cooked dinner over coals from a fire on the beach almost every night.