Great place on the beach to rent a surfboard or get lessons for all ages. They also have a brewery that has some of the best sushi we have had!
This site shows a lot of tours and activities within 2 hours of Tamarindo. There are other places to book that may be better but this gives a good idea of what there is out there.
This is a quieter beach across the river estuary from Tamarindo. Either take a small panga boat each way for $2 or by car it is 30 minutes. DO NOT SWIM ACROSS ESTUARY as there is crocodiles near by.
Quieter beach that connects to Tamarindo. Has lots of lava rock so it isn't good for swimming but beautiful for sunsets. 15-20 minute walk or a few minute car ride away.