Underwater-welding for marine maintenance and repair jobs bypasses the need to pull the structure out of the sea and saves much valuable time and therefore it is considered as an economical advantageous method when there is little time or due to operational requirements. The main difficulties in underwater welding are the presence of a higher pressure due to the water head under which welding takes place, chilling action of the water on the weld metal (which might change the metallurgical structures and properties), the possibility of producing the arc mixtures of hydrogen and oxygen in pockets, which might set up an explosion, and the common danger sustained by divers, of having nitrogen diffused in the blood in dangerous proportions.
Officer of the Watch 