Once O'Hara gave vent to a partly smothered yell as his naked foot came in contact with a slimy water-logged tree. It was easy to imagine unpleasant things in that modern Styx.
At the sound Denbigh turned.
"What's wrong?" he asked in a whisper.
"Nothing," replied the Irishman. "Carry on."
He was swimming rapidly. His quick strokes betrayed his acute anxiety to traverse the stretch of water in as short a time as possible.
"Steady; don't splash," cautioned Denbigh.
A reply to his admonition came from another quarter, for almost in front of the swimmers rose a huge black object, quickly followed by another. In the semi-light the two men could see that these were enormous hippopotami, distinguish even their thick lips and wire-like bristles, and hear the business-like snap of their formi
