Central and North American Surface Water Temps
Note that Costa Rica is located at approximately 9 degrees north latitude, and 83 degrees west. Surface water temperatures are shown in Celcius. For reference, the water is typically in the 26-30 degree celcius range (79-85 degrees fahrenheit).
Water is warm, and sun protection is a must. When in the water use plenty of sunscreen, lycra rashguards, T-shirts, and hats.
Data supplied by the NOAA.