The second need was vision. His host presumably possessed eyes, and with his oxygen supply assured the Hunter began to search for them. He could, of course, have sent enough of his own body out through the shark's skin to construct an organ of vision, but he might not have been able to avoid disturbing the creature by such an act. Besides, ready-made lenses were usually better than those he could make himself.
His search was interrupted before it had gone very far. The crash had, as he had deduced, occurred rather close to land; the encounter with the shark had taken place in quite shallow water. Sharks are not particularly fond of disturbance; it is hard to understand why this one had been so close to the surf. During the monster's struggle with the Hunter it had partly drifted and partly swum closer to the beach; and with its attention no longer taken up by the intruder, it tried to get back into deep water. The shark's continued frenzied activity, after the oxygen-theft system had been established, started a chain of events which caught the alien's attention.
The breathing system of a fish operates under a considerable disadvantage. The oxygen dissolved in water is never at a very high concentration, and a water-breathing creature, though it may be powerful and active, never has a really large reserve of the gas. The Hunter was not taking very much to keep alive, but he was trying to build up a reserve of his own as well; and with the shark working at its maximum energy output, the result was that its oxygen consumption was exceeding its intake. That, of course, had two effects: the monster's physical strength began to decline and the oxygen content of its blood to decrease. With the latter occurrence the Hunter almost unconsciously increased his drain on the system, thereby starting a vicious circle that could have only one ending.