We just got off the fantasy on the 2nd. We had no itinerary planned - we got in a cab ($8/pp) to cane garden bay. Another group in the cab went to Brewers bay. The cab driver stopped at Brewers bay first and we decided to get out there instead. While we never saw cane garden, we were completely enamored with Brewers bay.
Plenty of beach chairs for rent, a bunch of roosters running around and a shack with drinks for sale. The shack had a grill, but the grill man didn't show up...so the beach was emptying out because people wanted to buy food but couldn't. As a result, by 11am, we were sharing the beach with no more than 3-4 other families. The beach water was crystal clear, no algae, small lapping 6" waves - like out of a corona commercial. It was magical.
I've since learned that cane garden bay is the busier of the two beaches and Brewers bay is the quieter. It was perfect for us.
We ended up trying to recreate the magic by going to sapphire beach in st Thomas, the following day. Was not the same..it took forever to get there....was rockier, not as calm, then sapphire filled up with a cruise excursion by 11:30 and it was too crowded and noisy - so we bailed and it took 90 minutes to get back to the ship because of the crazy traffic in port due to 4 ships that were docked.
Tortola was amazing. Did not expect it, but it really was!