Surfing is the most popular sport in town, and you can easily rent boards and arrange transport – the town beach is surfable but not spectacular, and the good beaches are too far to walk to. Head for Remanso (to the south, and good for beginners), Maderas (to the north, popular with experienced surfers) or a number of further-flung options. Almost anywhere in town can arrange this – transport should set you back around US$5 and board hire about US$10. Water-taxis to playas Maderas and Majagual (12km to the north) leave from the area in front of Hotel Estrella at 10am or 11am daily, returning at 4pm or 5pm (40min; US$10 return) – a taxi will cost about the same.
The beaches, inlets and bays of the coast are ripe for exploration, and sailing and fishing trips are almost as popular as surfing – Casa Oro arrange backpacker-oriented fishing tours, and local tour companies all have trips of their own. San Juan isn’t quite the Corn Islands, but there’s still plenty of diving here: try Neptune Watersports.