Go on a little hike
The beach of Sóller is not really a place where you want to spend the whole day as it is not spectacular. But take a little hike and enjoy a great view to Puerto Sóller.
One hiking path starts right behind the left lighthouse. You get to the lighthouse in some 20 minutes if you walk slowly. From behind the lighthouse the hiking path is indicated very clearly. We took the "short" version which takes you a little around the "mountains" of Sóller and you get back out at Puerto Sóller. We made this hike in relaxed 1 1/2 hours. You can also hike to Deià which is a longer hike (2,5 hours oneway according to the signs) or even until the village of Sóller which is some kilometres from Puerto Sóller.