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 9 10 contain the special requirements applicable to three individual classes of weld: Class A - Comparable to above-water welding Class B - For less critical applications Class O - To meet the requirements of another designated code or specification