In his fish trap, Mafatu finally finds "three lobsters, blue-green and fat".
Mafatu had caught fish in his trap before, but more often than not, his catch had been stolen by a marauding tiger shark. Although he could ill afford to have his trap robbed,
"twice it had been broken into, the stout bamboos crushed and the contents eaten...often as he set his trap far out by the barrier-reef, the tiger-shark would approach, roll over slightly in passing, and the cold gleam of its eye filled Mafatu with dread and anger".
Mafatu actually catches the shark in the act of stealing one day when,
"as he approached the spot where the fishing trap was anchored, (he) saw the polished dorsal of the hated tiger-shark circling slowly in the water...it rushed at the bamboo fish trap and seized it in its jaws (and)...shook the trap as a terrier might shake a rat...the trap splintered into bits, while the fish within escaped only to vanish into the shark's mouth".
Mafatu finds the courage to jump in the water to attack the shark with his knife in a viscious fight to protect his dog Uri, who is in danger after being thrown from the raft. Mafatu emerges victorious, and from then on is able to use the sea creatures he catches in his trap for his own sustenance (Chapter 4).