In my opinion even better is Kelly's Beach in Kouchibouguac National Park. You just walk to the beach (only one way in) and then turn right and walk until you're out of site of the lifeguards. Then strip and enjoy the day.
I've been there maybe half a dozen times. It's a huge beach so you'll have as much space to yourself as you want and yet it's also fairly busy as its the main beach in NB's largest park with a camping site nearby. Lots of people walk the beach. Each time I've seen many nude people. Some even walking the beach too and none were ever hassled.
I highly recommend it along with Blooming Point, PEI, Crystal Crescent near Halifax and Martinique Beach in Musquodoboit Harbour, NS.
Don't know about any official groups in NB, but there is an amazing beach to go to, the Buctouche boardwalk sand dune.¿ It's not an official nudist place but if you walk to the end of the boardwalk, get off and keep on walking about another 10 minutes, there are lots of nudist sunbathers around.¿ Beautiful beach, not crowded, great place to spend the day.