Book excerpt: Many problems confronting the practicing commercial diver can be worked out easily and accurately with the use of the formulas provided here. Among the calculations given are those relating to decompression, fresh water vs. seawater, air supply, compass, and salvage. Pressure, volume, and temperature relationships, safe working loads of rigging and tackle, corrosion of metals, underwater light and sound -- all of these are discussed, supplemented by a list of useful references.