Hydrodat is a computer oriented system for storing and retrieving seismic shot-hole data. The system was initiated in 1967 by V.A. Carlson, who designed it and supervised its operation until the end of 1973. The objective of this report is to describe the system so that it may readily be used. The report consists of four sections: a description of how the basic data is compiled, a description of how new data is entered into the database, a description of how the Hydrodat system was established to facilitate the handling of large quantities of shot-hole data for use in the construction of bedrock topography maps of the province. All the data entered in the system was obtained directly from oil companies.