I tried Es Cavallet and was disappointed as there were only a few naturist couples on a huge beach, and it wasn't possible to swim.

Do get yourself over to Formentera - anywhere on the north east coast between the resort of Es Pujols (which is not a nude beach) and the northern tip of the island is my favourite bit. If you find the sea too wavy walk south and you will find a cove just north of Es Pujols.

It is possible to walk to these Formentera beaches from the ferry but consider hiring bicycles at the ferry port.

it's been 35 years since I have been to Ibiza but used to use beach if you are looking at Ibiza town from sea it's to the left.
Then there was a beach near cala Basa or Cala Conti, which is further up the coast same side, near san Antonio.
went to Formentera about 10 years ago, it's naturist until July to beginning of September when it's mainly textile.
Enjoy 🙂