Sometimes it was stationary, sometimes it was drawn taut.

The first great wave that came flung a yard or so of slack amongst them.

Then, after the roar of its breaking had died away, they saw the rope suddenly tighten, and pass rapidly out, and the excitement began to thicken.
"That 'un didn't get him, anyway," one of them muttered.
"He'll go through the next, with luck," another declared hopefully.
Lessingham, fighting for his consciousness, deafened and half stunned by the roar of the waters about him, still felt the exhilaration of that great struggle.

He looked once into seas which seemed to touch the clouds, drew himself stiff, and plunged into the depths of a mountain of foaming waters, whose summit seemed to him like one of those grotesque and nightmare-distorted efforts of the opium-eating brain.

Then the roar sounded all behind him, and he knew that he was through the breakers.
He swam to the side of the ship and clutched hold of a chain.