How Does Underwater Welding Work?

Written By: Liam Bryant

Underwater welding works the same way as standard welding, however, the current must remain shielded using flux, a shroud, or a hyperbolic chamber. 

Here is a closer look at how underwater welding works.

What Is Underwater Welding?

Underwater welding is used to complete welds on submerged structures and vessels. Welding underwater is often necessary when repairing marine structures, including dams, pipelines, oil rigs, bridges, ships, and more. 

A welder uses an electrode to create an electric arc that heats metal to the point where it becomes molten material. The molten metal cools and fuses. 

The welding process requires an electric current to pass from the electrode to the metal workpiece. Water contains ions that act as conductors of electricity.

Underwater welding requires protection against water to keep the current confined to the electrode and the work area. 

welding underwater

Types of Underwater Welding

The two main forms of underwater welding include dry welding and wet welding. Both options allow you to use various welding techniques to complete welds on underwater objects. 

Dry welding involves working with a shroud or chamber that protects the work area from the surrounding water. Wet welding involves welding underwater without a barrier to separate the weld pool from the water.

Dry Welding Underwater

Dry welding is a type of welding completed underwater inside a dry environment. Dry welding most commonly involves the use of a hyperbaric chamber.

A hyperbaric chamber is built around the work area. The welder and the welding equipment sit inside the chamber. 

The atmospheric pressure inside the chamber is kept at a slightly higher level compared to the pressure on the surface. Air is also continuously filtered through the chamber. 

Helium may be added to the inside of the chamber to help maintain air pressure and prevent the buildup of other gasses, such as nitrogen. 

The sealed, dry environment allows you to use almost any welding process, such as TIG or MIG welding. However, stick welding is also a common choice.

Stick welding eliminates the need for a separate gas tank, as the stick is coated in flux. It’s also more convenient than TIG welding, which requires you to hold a filler metal with a separate hand.

The use of hyperbaric chambers for dry welding is also called “habitat welding”. The habitat holds one or more welders. 

Habitat welding typically offers the best results when it comes to underwater welding. You can achieve higher quality welds thanks to the dry environment. 

Dry welding can also be expensive. The hyperbaric chambers are costly. 

Luckily, dry welding may also be completed with smaller shrouds placed over the electrode and the work area. 

The shroud shields the metal and the electric arc from water. The welder wears diving apparatus, as they don’t sit inside a hyperbaric chamber. 

Using a shroud is more common when dry spot welding. It involves a smaller setup, making it ideal for dealing with small repairs. 

Wet Welding Underwater

Wet welding involves welding underwater without a hyperbaric chamber. 

Wet welders use systems with direct current (DC) instead of alternating current (AC). The cables are also insulated twice to shield them against water. 

A stick welder is typically used for wet welding. Stick welding, or shielded metal arc welding (SMAW), relies on a consumable filler rod. 

The rod is coated in flux. As the rod and flux burn, the flux releases gasses that shield the electrode and weld pool. Small bubbles form that insulate the electrode from water. 

The bubbles allow you to weld underwater without shorting the welding machine or electrocuting yourself. However, the bubbles also limit your visibility. 

Wet welding may also be completed with the manual metal arc (MMA) welding process. The MMA welder uses an electrode with a waterproof coating.

Other suitable methods for wet welding include friction welding and flux-core arc welding.

Friction Welding Underwater

Friction welding uses friction to generate heat instead of relying on a consumable filler metal. It’s also called solid-state welding or underwater friction stir welding (UFSW), depending on the method.

Friction welding doesn’t require a filler metal, which makes it more convenient for underwater welding. It also works with a variety of metals, including:

  • Aluminum
  • Brass
  • Bronze
  • Cast iron
  • Copper
  • Lead
  • Steel alloys
  • Tungsten

Yet, friction welding is only suited for use with smaller parts. It’s often used when securing small parts onto larger assemblies or welding bolts into place. 

Flux-Core Arc Welding Underwater

Flux-cored arc welding (FCAW) is a common choice for wet welding, as it produces higher-quality underwater welds. 

The electric arc in FCAW is created using a continuously fed filler metal. The filler metal contains a core comprised of flux.

Flux is a chemical agent that protects the metal from oxidation. It also shields the molten metal from water during the welding process.

Dangers of Underwater Welding

Underwater welding brings added risks compared to standard welding on land. One study found that the fatality rate for welder-divers is 40 times higher than the national average

Here are some of the biggest dangers of underwater welding:

  • Electrocution 
  • Explosions
  • Decompression sickness
  • Drowning
  • Freezing
  • Marine life

The dangers of underwater welding include electrocution, no matter the method used. All equipment needs waterproofing to shield it against exposure to water and moisture.

Water can conduct electricity, so you must keep electronics away from liquid. This is also true when welding underwater.

Welder divers should always inspect the equipment before use to reduce the risk of electric shock and electrocution. 

Underwater welding also creates the risk of explosions due to the use of combustible or flammable gasses, such as hydrogen and oxygen. 

The buildup of flammable gasses may eventually cause an explosion, which is why underwater welding requires ventilation. Underwater habitats require the use of large fans to circulate air constantly. 

Welder divers can also suffer from decompression sickness, commonly called “the bends”. This occurs when dissolved gasses create bubbles inside the body. 

Decompression sickness can cause fatigue, muscle pain, numbness, and difficulty concentrating. It can also prove fatal.

Decompression sickness is more common when returning to the surface too quickly. The sudden change in pressure interferes with your body’s ability to use excess nitrogen. 

Welder divers should avoid ascending quickly. They should also stay hydrated and avoid drinking alcohol before diving. 

Working underwater also includes the risk of drowning. Drowning is the leading cause of death for welder divers.

Workers can become entangled in cables and struggle to return to the surface. This is why welder divers should always pack a knife. 

A common safety tip is to avoid panicking if you become entangled or lose access to oxygen. Maintain a calm head and reduce your breathing speed. 

Deep diving may expose welder divers to freezing temperatures. The water gets colder the deeper that you go. 

Always check diving equipment for tears. Water reaching your skin may quickly reduce your body temperature, which can lead to hypothermia and respiratory issues. 

Marine life can pose a threat to workers. Welder divers should pay attention to sharks and other marine life. Marine life may result in delays or distractions even when not posing a direct threat.

underwater welding

Reasons to Weld Underwater

Underwater welding is a common task for commercial divers. It’s a necessary task for repairing large submerged or partially submerged structures, such as:

  • Boats
  • Oil rigs
  • Underwater pipelines
  • Dams
  • Bridges

Underwater welding is often the only way to carry out emergency repairs. Removing one of these structures from the water isn’t always an option. 

Equipment Required

The equipment required for underwater welding depends on the method used. Dry welding may require a hyperbaric chamber or a shroud. 

Welder divers may also need the following equipment for dry or wet welding techniques:

  • Diving suit
  • Diving helmet
  • Umbilical cord/air supply
  • Harness
  • Diving knife
  • Power supply
  • Welding gun 
  • Waterproof electrode

When welding underwater, a diving suit, helmet, and other diving gear are needed. Welder divers typically use standard diving helmets. A welding screen is added to the front of the helmet to shield the eyes.

Welder divers almost always receive the air supply from the surface. The umbilical cord supplies air.

A harness keeps the diver in one spot as they work. They also need a diving knife, which is used to deal with various tasks, including cutting cables should you become entangled.

The power supply, welding gun, and waterproof electrode are used to carry out the welding task. 


Dry welding and wet welding are the two main categories of underwater welding. Dry welding involves the creation of a dry environment around the area that needs welding. The work area is shielded from the water with a shroud or enclosure, such as a hyperbaric chamber.

Wet welding involves welding without encapsulating the work area. The electrode is insulated against water while the flux in the consumable provides added shielding. 

Underwater welding also comes with risks, including electrocution and drowning. However, underwater welding is often the most economical way to complete emergency repairs on seagoing vessels and structures. Instead of dry docking a boat, you can send a welder diver to repair it.