In situ measurements were undertaken during two non-upwelling periods (15 days in June 2012 and 7 days in May-June 2013) at a water depth of 1.5 m. pH, pCO2 and seawater temperature were measured with two Submersible Autonomous Moored Instruments (SAMI-pH and SAMI-CO2, deployed at the pier of Marina Papagayo (10.64154,-85.65571). Discrete water samples were used to validate the sensors, and salinity values were obtained from discrete water samples and used for correction of pH values. Wind speed data was obtained from a station of the Instituto Metereológico Nacional (National Metereological Institute of Costa Rica) located at the nearby Liberia airport. Tidal data was provided by Módulo de Información Oceanográfica of the University of Costa Rica.