Submerged Arc Welding (SAW) is an arc-welding process in which a continuously fed bare consumable electrode wire forms an arc with the workpiece, but the entire arc and molten weld pool are buried beneath a mound of granular flux deposited ahead of the weld. The name "submerged" refers precisely to this: the arc burns hidden under the flux blanket rather than in open air.

The flux layer serves several roles. It melts near the arc to form a protective molten slag that, along with the unmelted granular flux above it, completely seals the weld zone from the atmosphere, keeping out nitrogen, oxygen, and moisture that would otherwise cause porosity and embrittlement. It also concentrates the heat, which gives SAW its characteristic deep penetration and high deposition rate, and it can add alloying elements and deoxidisers. Because the arc is covered, there is essentially no visible arc flash, no spatter, and greatly reduced fume and radiation.

Therefore the statement that best describes the arc is that it is completely covered by a layer of flux.

• The arc is exposed to the atmosphere is wrong — the flux specifically prevents atmospheric exposure; open-arc behaviour is more typical of processes like SMAW.
• The arc is shielded only by inert gas describes gas-shielded processes such as MIG/TIG, not SAW, whose shielding comes from the granular flux and its molten slag.
• The arc is visible and produces bright light is exactly what SAW avoids; the buried arc gives no bright visible flash, which is a key operator-safety benefit of the process.

Hence the arc in SAW is completely covered by a layer of flux.