To get here, you end up driving almost to Udall point and park on the right side of the road. It looks like a lookout parking spot. There is a path to the right of where the cars can park... It only fits about 7 cars. The trail is fairly good to Isaac's Bay, just watch out for some of the thorn bushes. If you want to continue to Jack's Bay, and this is very important, make sure to go down onto Isaac Bay via the wooden stairs and walk to the end of Isaac Bay beach before heading back up on the trail! If not, you will be very sorry, and end up traversing a very poor "trail" and wish you had heeded my advice. We made the mistake of continuing on and didn't notice the easy way until we saw the horrendous beach that is Jack's Bay and turned around to hike back to Isaac's. You have been warned.
We went in early June 2014. The weather was very nice, the water was nice and refreshing. The waves were small and the bay is sheltered by coral. There was a nude man there at the beach when we went, just a word of caution. You might want to stick near the wooden stairs that lead down to the beach if you want to avoid that sort of thing.
The beach is sandy, you do have to find places to enter the water that are sand and not rock/coral. There are plenty of those places, just a word of warning.
There is nothing out there... no toilet, no food, no phone, nothing. We brought a cooler and were very happy to have food and drinks. NO GLASS! Please, nobody likes stepping on glass, and no matter what you say accidents happen and you can end up breaking the bottle and ruining someone's vacation.
If you are not in good shape, I would suggest not looking at Jack's Bay, just hike the 2 miles to Isaac's Bay and enjoy. If you enjoy hiking, by all means go to Jack's and beyond. Remember water!
The snorkeling is ok at best. I saw a few small squid, and a lobster. That was about it besides the coral reef fish that you can see almost anywhere... trigger fish, parrot fish, etc. There are only a few nice pieces of coral spread out over a wide area. Waves break on the barrier coral and father in, most of the coral is splotchy all over the place. I enjoy snorkeling and have been to many different places and I ONLY snorkel. I do not dive. There is better snorkeling at St. Johns.... anyway, it is what is is... and we had a very nice time, even if I wish the snorkeling had been better. The water was nice, the day was nice, and we brought a nice lunch.
Keep your expectations low for snorkeling and enjoy the beach with a few other people, it that.