The paper describes the experimental findings of underwater wet welding and cutting of API X70 pipe steel and plates with the use of the following flux-cored wires: TiO2-CaF2; Fe2O3-TiO2 and Fe2O3-TiO2-SiO2. For cutting the cored wire with a diameter of 2 mm based on salts of iron and alkali metals was developed. The best weld properties have been achieved during the underwater welding with fluoride flux-cored wires with TiO2-CaF2 system, which provides the suitable micro structure of the weld, high solidity of deposited metal and mechanical properties of the weld. The use of flux-cored wire improves a quality of underwater wet cutting of steel plates with thickness up to 8 mm.