Notably off-the-beaten-path despite being less than an hour's ride from the Son Sant Joan International Airport, Cala Mondrago Natural Park is a destination for those who value beautiful ocean landscapes without needing the best in modern tourist amenities. It is also one of the rare corners of the island where there isn't public transport from the airport, meaning that you'll have to pay for a taxi or rent a car yourself. The park itself is a preserved area of wetlands and dunes, but the main draw is the beach, which is bordered on both sides by rocky bulkheads and is the epitome of Mediterranean sand and water.
There are two inexpensive hotels and a few restaurants near the water and, since the beach does tend to get busy on the weekends, you can easily walk to the more secluded S'Amarador beach if you're looking to escape the crowd. Be sure to wear comfortable shoes if you're actually looking to enjoy more than the swimming and sun; stop in at the park entrance for a map of the handful of hikes that are available, the longest of which will provide you a half day in one of the rare preserved areas that still remain on Mallorca.