If I had only one day in N. Sound I'd probably spend the morning snorkeling the reef (try to find the cannons) then I'd check out Saba for a drink. I haven't been impressed there (and not even with the bar drinks) but I feel like you should at least pull up for a drink and a round of pool. It's not anything like it was but one can still appreciate the location. From there I'd jump to BEYC for lunch. Happy hour if Saturn is on is quite fun. Starts at 3pm. I would then do Leverick Upstairs for dinner. Or if you plan it on a Fri, do the beach BBQ/Jumbies. Fun night with good food for only 40/pp.
Depending on the day you are there you could also start your day with the oil nut brunch, then snorkel out there and then hit the other spots as mentioned.