On one of my recent visits to the Algarve, I enjoyed a great day out on the Island of Armona, a short ferry ride from the quayside in Olhao, just east of Faro.
With its near deserted beach on the far side of the island, it is definitely worth a look.
The whole outing is easily managed in a day. When you arrive at the quayside there are a few restaurants here to choose from if you like the idea of some lunch before hitting the beach. Fish obviously scores highly on the menus, but there are other options too.
Although there are beaches all around you, the most beautiful one is on the other side of the island, and worth the walk. Take the main street, lined with pretty bougainvillea covered cottages, that leads from the jetty all the way across the island to the near deserted beach on the other side. Waters are calm here as you are within the Ria Formosa Nature Lagoon.
It is about a half an hour walk along the main street and onto the wooden walkway leading to the beach. If you want to stay a bit longer and don't make the ferry back, then do like we did, and get a little water taxi, which was fast (!) and good fun. You can ask at the restaurants for someone to call you a water taxi.