During the past decades, Ocean Bottom Seismometers (OBS) have played a key role in permanent seismic activity monitoring at sea as well as allowing a better understating of the earth interior. Data collected by the instrument can provide information on the ocean bottom sub-layers down to a depth of 40 km beneath the ocean floor. The accuracy of the results directly depends on the temperature stability of the crystal used as the main time base of the equipment. This paper presents the study of temperature stability of a Seascan module in real environmental conditions. By means of a climate chamber, temperature tests of a Seascan module were carried out and crystal temperature stability was calculated.