MILA is a Marine Internet Laboratory for the study of different transmission techniques in marine conditions. For the tests, the laboratory has an external water temperature sensor that is installed approximately 0.5 m below the waterline. The measuring device is based on Sodaq One (Arduino compatible). The system is powered by a lithium polymer battery with a capacity of 350 mAh and a rated voltage of 3.3 V. In addition, the system is equipped with a solar cell to extend the battery life. During our research, the working time of the prototype measuring device was about 5 hours.