Kind of a shore break here so no real surfing so to speak but you can do some fun body whomping in the shore pound..watch the rips though as they are frequent here. Best time to swim in in the morning prior to 11 or after 3pm when the sand starts to cool down. From 11-3 the black sand is a bit on the hot side to walk on barefoot.
If you stay at ARCAS during turtle season you will do plenty of this. There are a few other hatcheries near Monterrico. ARCAS does releases based on when the turtles are ready while some of the other places will hold hatchlings for tourist releases..ARCAS is more pro-turtle so to speak.
Wildlife volunteers (you can be one!) help the University of San Carlos workers release baby turtles from hatching area to ocean. They hold a competition with tourists to see whose turtle makes it first to the water (all are released humanly) it is facinating to watch and participate. Also get guided bird watching tours. Several locals offer fishing trips and it is possible to catch a Marlin or MahiMahi.. Go for it....coooool. Dj
The locals love beach soccer and in the village of Hawaii they have a championship team. If you are around during a festival you will probably see a game...Look for the Gallo tent and the noise.