I doubt they had many people violating the exclusion zone in sailboats. Regardless a 500 or 1000 dollar fine would be sufficient. A daytime exclusion zone serves no function at all as far as Covid. At night perhaps but it would only be people intending to go ashore and or remain illegally in the BVI that would present a problem. Mostly that would be locals shopping and avoiding import duties. I once spent the night in water lemon cay. A friend brought a handheld nightscope. It looked like a highway running from the USVI and BVI. I was surprised there were not collisions with all those boats and no lights!
G