"The power of thought was restored; he knew that the rope had broken and he had fallen into the stream. There was no additional strangulation; the noose about his neck was already suffocating him and kept the water from his lungs." 

"He had come to the surface facing down the stream; in a moment the visible world seemed to wheel slowly round, himself the pivotal point, and he saw the bridge, the fort, the soldiers upon the bridge, the captain, the sergeant, the two privates, his executioners. They were in silhouette against the blue sky. They shouted and gesticulated, pointing at him. The captain had drawn his pistol, but did not fire; the others were unarmed. Their movements were grotesque and horrible, their forms gigantic.

Suddenly he heard a sharp report and something struck the water smartly within a few inches of his head, spattering his face with spray. He heard a second report, and saw one of the sentinels with his rifle at his shoulder, a light cloud of blue smoke rising from the muzzle. The man in the water saw the eye of the man on the bridge gazing into his own through the sights of the rifle. He observed that it was a grey eye and remembered having read that grey eyes were keenest, and that all famous marksmen had them. Nevertheless, this one had missed.

A counter-swirl had caught Farquhar and turned him half round; he was again looking into the forest on the bank opposite the fort. The sound of a clear, high voice in a monotonous singsong now rang out behind him and came across the water with a distinctness that pierced and subdued all other sounds, even the beating of the ripples in his ears. Although no soldier, he had frequented camps enough to know the dread significance of that deliberate, drawling, aspirated chant; the lieu. tenant on shore was taking a part in the morning's work. How coldly and pitilessly--with what an even, calm intonation, presaging, and enforcing tranquillity in the men--with what accurately measured inter vals fell those cruel words:

"Attention, company! . . Shoulder arms! . . . Ready! . . . Aim! . . . Fire!"

Farquhar dived--dived as deeply as he could. The water roared in his ears like the voice of Niagara, yet he heard the dulled thunder of the volley and, rising again toward the surface, met shining bits of metal, singularly flattened, oscillating slowly downward. Some of them touched him on the face and hands, then fell away, continuing their descent. One lodged between his collar and neck; it was uncomfortably warm and he snatched it out."

I find the physical condition of this man to be unusually good after he submerges from the water. The soldiers probably began shooting at him within  seconds of his sumbersion and he is already able to dive back under water and hold his breath again. I t seems that after having a rope squezzing your neck it would have been hard to breathe properly. I dont know much about hangings. Do you know if the rope is very tight around the crimanl's neck before they are hanged. Or is it loosley secured around the criminal's neck?