Here is what I found from other posts-
We actually usually hike to the Piscines Naturalles which (correct me if I'm wrong) are near, but not the same as "The washing mchine". What I know about the washing machine is...don't go swimming there - way too dangerous!! The Piscines Naturelles (natural pools) are very safe, it's just quite a hike to get there. Drive to Grand Fond, park in the little parking lot near the dumpster, walk down the public beach access path (the one with barbed wire on each side). When you get to the beach, take a right. Walk down the beach to the rocks. Climb up the rocks and find a poorly marked path that continues along the rocks in the same direction you've been heading. Walk about 25 minutes, you'll see spectacular views of waves crashing into the rocks below (per chance this is the washing machine - certainly waaaay to dangerous for swimming). When you get to a point where the rocks have formed peaceful, tranquil natural pools, climb down and explore. It is truly an enchanting area, just watch out for the sea urchins.
"The highlight of the trip was our discovery of a natural swimming pool in Grand Fond. The driver at Le Toiny pointed out the path on our way to the hotel and it was one of the most beautiful spots I have ever seen. The hike begins where the road makes a sharp left along the ocean in Grand Fond. Walk right when you get to the beach and climb up the rocks at the far right side of the beach to the goat path. Hike along the ocean for about 15-20 minutes (it isn't that steep but you are up pretty high) and you'll come to a rock formation where the water is protected from the waves (which are impressive on this side of the island). A couple of small, natural swimming pools have been formed by the rocks and the water will fizz as the waves crash against the rocks -- it is stunning. We did the hike/swim twice and never saw another person."
As to how to hike to the secluded beach (Washing Machine) at Grand Fond, the road from La Petite Saline was closed in June when we were there last, so we drove the long way round past Anse Toiny to head southwest to Grand Fond. Just after the road turns right (northwest) to leave the shore, there is a small parking area on the left. Park there and walk back toward the shore. Take the long, narrow public access walkway to the stony beach of Grand Fond, then go to the right to the end of the beach. It won't look like it, but there is a path that lets you climb up onto the headland, where there is a trail above the shore going south. After 20 or 30 minutes of hiking, you'll see a white sand beach below, with several paths to get down to it. There are lots of large rocks on the beach and in the water, so swimming would be dangerous if there is any kind of surf running. But the beach itself was completely empty when we were there. This is not one of the traditional/recognized clothing optional beaches (those are Saline and Gouverneur, at the appropriate ends), but there are so few people that hike here, and the setting is so deserted, that I can't imagine any problem in going nude, even if some hikers might see you from the path above.