Sark is a plateau island, therefore most of the beaches involve a combination of steps and paths which can be fairly steep.
Derrible is best for the beach at low tide but it is lovely swimming off the rocks at high tide.
Dixcartis lovely especially at low tide when the sand is exposed, also the most easily accessible. For shelter, try this one if the wind is northerly.
Creux Harbour is very popular with local children and families. Take care to keep away from boats. Not suitable for swimming at low tide. The only beach with a café (and toilets) nearby! For shelter, try this one if the wind is westerly.
Derribleis a beautiful sandy beach at low tide and at high tide you can swim off the rocks. Quite a long route down (and up!) but well worth the effort and great for snorkeling. Caves to explore at low tide. The path is close to the cliff edge, so take care with children. For shelter try this one if the wind is northerly.
Greve de la Ville is gorgeous at high tide in the morning. For shelter try this one if the wind is westerly.
Port du Moulin is best from half tide up to half tide down. Pebbly cove. Excellent for snorkelling. Go through the rock arch on the right to swim in a tiny cove around half tide, but be careful not to get cut off by the tide. For shelter try this one if the wind is easterly.
Eperquerie Landing is a small pebbly bay just north of the landing. Be careful on the large slippery rocks. For shelter try this one if the wind is south westerly.
Venus Pool is in Little Sark, but quite difficult to find. A natural rock pool deep enough to swim in. Accessible two hours either side of low water. Lovely flat rocks for sunbathing. Path to pool is very sheer and can be slippery and dangerous. For shelter try this one if the wind is northerly.
Port Gorey is in Little Sark. Deep water, and good for fishing. For shelter try this one if the wind is north or easterly.
Havre Gosselin Small landing, deep water. Steep path. For shelter try this one if the wind is easterly.
As well as those above, there are numerous other small coves and rock launching platforms which you may find. If you are jumping in, always give some prior consideration to the depth and how you are going to get out. Rocks covered with seaweed can be very slippery and a swell can make climbing out tricky.