I had to laugh reading some of the reviews about the "crowds." I think the reviewers have probably never experienced the beaches of Maine or Cape Cod during the summer months. The "crowds" I experienced at Trunk Bay couldn't hold a candle to the crowds at the Cape during summer...and that's with sharing the beach some days with snorkeling groups and cruise passengers.
My GF and I planted ourselves at Trunk for at least four of our 12 days on St. John. Each morning we would get there before 10 and have our "pick" of spots. The sun gets blistering hot, so get there early to assure yourself of a shady area. We never felt the beach got too busy or too crowded. In fact, the people seemed to come and go in waves. For a few hours, there would be a big snorkeling crowed. Suddenly they would be gone and a new crowd would come a few hours later. We never had a big wait at the concession stand and we never had a problem with the birds stealing our food, either! Although we did have one hilarious incident in which a bird (someone called it a brown boobie?) landed beside our blanket and dropped a lizard it had caught. The terrified lizard than bolted, fast as lightening, up my GF's bathing suit bottoms. Once she was able to maintain a regular heart beat, it was hilarious (the lizard fell out the moment she stood up and screamed).
Being novice snorkelers, we loved the underwater trail and loved snorkeling! We saw a sea turtle, a sting ray, squid, and a hundreds of beautiful fish. There are lots of signs around instructing tourists not to feed fish, not to stand on the coral, etc. Sadly, we kept witnessing people doing just that. I guess our biggest peeve with Trunk had nothing to do with the beach itself, but with some of it's visitors. Apparently, a lot of visitors think they are above the rules. But anyway, I am off the subject.
Trunk Bay is picture post card perfect. We loved it!! We hope someday to visit again.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC