In Plakias you can find travel agencies offering excursions and visits for the main attactions on Crete island. You can visit gorges like Samaria gorge, archeological sites like Knossos, interesting beaches like Elafonisi or Preveli palm beach and many other destinations.
If you prefer to walk in nature surrounding Plakias, then you can download the PDF version of the book from Lance Chilton and Marengo Publications 1998, that is not any more available in commerce:
Ten walks in the Plakias area

Plakias is offering plenty of choices in order to make interesting tours in the sea. You can rent a small boat yourself, make trips for fishing or to discover beautiful destinations in the rich and beautiful southern coast of Crete island, like Frangokastello, Preveli palm beach, Loutro, Marmara and many other