We did See Antigua by Sea twice on our B2B in April/May this year.
It was the best excursion. Its a catamaran ride all the way around the island and they have 2 beach stops as well with snorkeling. BBQ lunch and free drinks both alcoholic and non alcoholic included in the price. I will tell you when the boat hits the Eastern part of the Island it gets rough, its about 15 minutes or so of some super choppy seas, I was on Bonine or I would have not faired well. But we loved it so much we did at both Antigua stops.