Tamarindo beach on first sight is obviously a surf destination.  Surf shops make up a huge percentage of the stores and there are lots of surfboards available for rent. Local surf breaks outside of Tamarindo include Langosta, Playa Grande, Avellanas, and Playa Negra.

 Kelly's Surf Shop

Witch's Rock Surf Camp 

 Try them out for lessons and surfboard rentals.

Check Costa Rica Surf Club for a surf map of the area or pick one free at the surf shop, keep an eye on tide changes while you surf over the reef's ask for advice on where to go surf for your level. 

Matos Surf Shop (Sunrise Mall No 4 and 506-2653-0845) and were handled by Eric. Great guy