We drove from Liberia to Playa Grande on the Peninsular and booked onto the turtle observation at the office of Parque Nacional Marino Las Baulas de Guanacaste.
We then went to have a 2 hour surf lesson with Frijoles Locos surf shop ($30usd each). We haven't been on boards for a couple of years, so we definitely needed the confidence boost and the instructors were laid back and had plenty of experience. Recommended. Playa Grande has consistent waves and the area is quiet, so it's ideal for those with a bit of experience, but need to practice. The famous dive sites Witches Rock and Ollie's Point are for experienced surfers only though...and very pricey excursions.
We then found a secluded beach for the night, watched the sunset and had a BBQ. Already in love with Costa Rica.