He--" The Master's babbling jaw fell slack; and the pleased grin faded from his face.
Wefers had come to the surface, after his ducking.

He was fully three yards beyond the dock and as far from his drifting scow.

And he was doing all manner of sensational things with his lanky arms and legs and body.

In brief, he was doing everything except swim.
It was this phenomenon which had wiped away the Master's grin of pure happiness.
Any man may fall into the water, and may present a most ludicrous spectacle in doing so.

But, on the instant he comes to the surface, his very first motions will show whether or not he is a swimmer.