Dave caught it easily enough.

Then, still sitting on the raft, his legs, of course, in the water, Darrin recoiled the rope.
"Can you spare a hand to catch, Dick ?" shouted Dave.
"Surely!" came back the steady answer.
The coil flew out across the thin ice.

One end splashed in the water.

Guiding the all but helpless Fred, Dick swam to the rope's end.
Further back the two men who held to the rope connecting with Dave had seated themselves across the second raft.

If the ice broke at _that_ point they would have little difficulty in making themselves safe.
"Ripley, stir yourself!" ordered Dick.