As before, now Sunfish battled as seemed to him best, for Thurston, astride behind the saddle, held Mona somewhat tighter than he need to have done, and let the horse go.
So long as Sunfish had footing he braced himself against the mad rush of waters and forged ahead.

But out where the current ran swimming deep he floundered desperately under his double burden.

While his strength lasted he kept his head above water, struggling gamely against the flood that lapped over his back and bubbled in his nostrils.

Thurston felt his laboring and clutched Mona still tighter.

Of a sudden the horse's head went under; the black water came up around Thurston's throat with a hungry swish, and Sunfish went out from under him like an eel.
There was a confused roaring in his ears, a horrid sense of suffocation for a moment.