Together they walked to the stern of the disabled craft. One look at the propeller shafts, the examination being made by the diffused glow from the searchlight, as well as from the electric torches carried, showed that the diagnosis of the trouble was correct.
Wound around both propellers was a mass of the serpent weed, tightly bound because the machinery had whirled it around and around after the grass had once been caught. It was almost as bad as though manila cable had been thus accidentally fastened.
"Well, might as well begin to cut it loose," said Tom to his companions. "Koku, you take the port propeller, and Ned and I will work on the other. You ought to be able to beat us at this game."
"Me do," said the giant, as he got his axe ready for work.
Blows struck in water lose much of their force. This can easily be proved by filling a bathtub full of water, rolling up the sleeves, and then taking a hammer in the hand, immersing it fully, and trying to strike some object held in the other hand. The water hampers the blows.
It was this way with Tom and his friends. Nearly half of Koku's great strength was wasted. But they knew they could take their time, though they did not want to waste many hours.
The streamers of weed were like strands of tightly wound rope, and this, under certain circumstances, acquires almost the density of wood. Tom and Ned, working together, had managed to chop a little off their propeller shaft, and Koku had done somewhat better with his task, when Ned became aware of a shadow passing above him.
Instinctively he looked up, and as he did so he could not repress a start of horror. Tom, too, as well as Koku, saw the menacing shadow. Ned grasped more tightly his sharp, steel bar and spoke through the telephone to his companions.
"Devil fish!" he said. "The devil fish are after us."