Its was in 1971 in Canada that the DCIEM or Defence and Civil Institute of Environmental Medicine was founded in a joint participation of military and civilian personnel. This lead to the development of dive tables that were more conservative than the US Navy tables.
The dive tables were invented to deal with the effect of surrounding pressure that increase the nitrogen dissolved in our body. They were the first way to calculate times and depths to dive safely and prevent decompression sicknesses. Nowadays computers applies almost real time the calculations made to create the tables.