This paper is based on assessing measuring devices (data loggers) which are used for temperature measurements in sublittoral caves ranging from 0°C to 30°C. The collected data, measured in the cave Poganica on the island of Šolta between 2008 and 2012, are also processed. In the first part of the paper a calibration of data loggers in six points: 0°C, 6°C, 12°C, 18°C, 24°C, 30°C was carried out. From those results the measurement uncertainty was calculated. It turned out that the deviation of data loggers are small at all points. Standard platinum resistance thermometer Pt 25,5 is used. The calibration was carried out at the Faculty of Mechanical Engineering and Naval Architecture, whose Laboratory for Process Measurements is the holder of national standards for temperature, pressure and humidity. The second part of the paper refers to processing the data measured in the cave in order to check whether the devices had, after specific time in cave, lost their accuracy. It had been planned to track the delay of maximum temperature inside the cave from the one at the entrance to the cave. However, it turned out that the problem was much more complicated and it is not possible to determine the accuracy of the devices in this way. The heat transfer between warm and cold water occurs in different parts of the year and there is no way to determine a scheme that can be applied in all situations.