If you use a Mares Puck, it automatically logs your dive info for you. Date, depth, time, and water temp are all stored. Also, I purchased the additional dive log software and cable ($50) to transfer the log data to my pc. There I can view a graph of the dive profile, and add any other info I want (i.e. dive location, weather, current, water clarity, dive buddy, notes, etc.) Well worth the $50.