This specification covers the requirements for welding structures or components under the surface of water. It includes welding in both dry and wet environments. Sections 1 through 6 constitute the general requirements for underwater welding while sections 7 through 10 contain the special requirements applicable to four individual classes of weld:

Class A - Comparable to above-water welding

Class B - For less critical applications

Class C - Where load bearing is not a primary consideration

Class O - To meet the requirements of another designated code or specification