Find out how we patch up holes in vessels and pipes in a watery environment Joining and fusing materials together has been a key part of engineering for centuries, but what about doing it underwater? High-pressure welding, more formally called hyperbaric fabrication, can now be undertaken in water in two ways. Dry welding is done in a closed chamber, while wet welding can join metals completely exposed to water. An example of a dry welder is the Deep Rover submersible. Primarily used for exploration, this vehicle can hold up to two people in a sealed sphere and is capable of lifting chunks of metal too. Wet welding, on the other hand, creates a bubble of carbon dioxide around the weld point while the repair is made. Dry welding is safer due to the added protection but tends to be more expensive and time-consuming. Therefore, dry is better for larger, more involved projects while wet is generally used for smaller tasks. Both are used primarily t...