Underwater Welding also known as Hyperbaric Welding, involves two specific types of welding, one called ``wet`` underwater welding and the other "dry" underwater welding. Even though they sound almost the same, different techniques are involved when performing these two types of welding, specifically because of their surroundings. Both are equally important when underwater construction occurs, or when marine maintenance is needed for pipes or ships.

Wet Underwater Welding occurs when the diver is introduced directly into the water making this their entire environment. There is no type of barrier between the welder/diver and the surrounding water, so the welding equipment and power supply is connected through cables and hoses. However, with dry underwater welding, the welder/diver is divided from the surrounding water. They may start welding in a pressure vessel or a large chamber where water is displaced. Two things needed when performing either type of welding are: the person should be a skilled diver and a skilled welder.