Swaine was not left long in doubt as to the stranger's intentions. Apparently the other diver was as surprised as he was, for he halted, swaying slightly in the comparatively feeble current. Then, slowly fumbling, he drew out a knife that showed a pale, dull-greenish glint in the subdued light. Courageous though he was, Swaine felt his heart beating violently. He was still undecided as to whether the stranger intended sticking the point of the steel into him or whether he meant to cut the guide-rope. In any case, Swaine realized that he would have to act on the defensive. Drawing his own knife, Swaine, holding on to the rope with his left hand, planted his feet firmly and threw his weight slightly forward. Then he awaited developments. He was handicapped by the fact that his air-supply was now noticeably weak. He might, with discretion, attempt to elude his antagonist, but he realized the disadvantage of showing his back to a man who might possess a greater degree of mobility. Nor did he fancy a knife-thrust as he was in the act of blowing himself to the surface. No, the issue had to be decided there and then. Holding his knife dagger-wise across his chest, the unknown assailant advanced. Swaine stood on the defensive. He was in an awkward predicament, for the current that was helping his opponent was against him. The other feinted. It was a comparatively slow movement compared with the lightning-like thrust of a practised fencer. The pressure of the water was too great for rapidity of action. Swaine was not prepared for what followed. His antagonist arrested the blow and at the same time hacked ponderously with his leaden-shod boot. The metal rasped on Swaine's bare knuckles grasping the rope, as he stepped backwards to avoid the full force of the blow. The next instant a cut with the keen blade of the other's knife severed the guide-rope. The sudden release of the tautened rope sent Swaine staggering a good three yards. He found himself sprawling on the sandy bottom, his efforts to regain his feet disturbing the sand to such an extent that it was almost impossible to see anything beyond arm's length. Not daring to transfer his knife from his right hand to his left, Swaine fumbled for the release-valve of the buoyancy-flask. His fingers, numbed with the glancing blow they had received, were almost useless, and his head was swimming with the effect of the now impure air. Before he could attain his immediate aim he saw the distorted figure of his antagonist through the now clearing water. Still struggling to regain his feet, the while guarding himself with his knife, Swaine realized that the odds were very much against him. He found himself vaguely wondering what the effect of a thrust would be through the thick rubber and canvas fabric of his diving-suit. All the same, he meant to stick it, and, if needs be, "die game".