"It looks too shallow to take anything more than a flat-bottomed light-draught vessel," remarked Hythe. "Still, as you say, sir, we ought to leave nothing unexplored behind us. If you wish I will take charge of the whaler and see what it is like." "Very good, Mr. Hythe. I shall be obliged if you will. We’ll remain here. Do not proceed further than there is depth for the ’Aphrodite’ to follow. Should you require assistance fire three explosive rockets. If anything should necessitate your immediate return I will make a similar signal. Should you locate the ’Vorwartz,’ endeavour to return without being seen." It certainly required plenty of zeal to volunteer for a boating expedition on a tropical river in such torrential rains, but the men called upon for the service responded with alacrity. Four rowers stripped to the waist sat on the thwarts, apparently quite indifferent to the rain. Hythe, Polglaze, and Carclew were in the stern sheets, partially protected by an awning, but before the whaler pushed off the canvas covering, sagging under the quantity of rain water, was found to be of more trouble than use, for a regular stream poured through the canopy upon the sub’s head and shoulders. Since it was also likely to attract the attention of Karl von Harburg’s men Hythe ordered it to be struck, and accepting the situation as well as he could, was soon soaked to the skin. The tributary was found to be nearly twenty feet deep towards the right-hand bank. On both sides were belts of malodorous mud on which numerous crocodiles were lying as if enjoying the rain. Others, looking more like floating logs, were drifting in the channel, and careful steering was needed to avoid them. Hythe realized that he was not on a sporting expedition, and should any of the saurians become infuriated it would be necessary to fire at the reptile. The report of the rifle would give the alarm to the "Vorwartz" should she be within hearing, and the chances of locating her without being discovered would be very remote. For more than a mile the rowers toiled manfully. The current was strong, the boat heavy, while Polglaze had to bale incessantly to prevent the rain from rising over the stern gratings. The "Aphrodite" was now lost to view by an intervening bend in the course of the stream. The depth still continued regular, and afforded plenty of water for a craft like the "Vorwartz" to ascend if her ballast tanks were emptied, but as reach after reach was opened out no sign of the rival submarine was visible--only a monotonous stretch of coffee-coloured water enclosed on either hand by the soft stagnant mud that effectually prevented any attempt at landing. "What’s that, sir?" asked Polglaze, suddenly holding up his hand and listening attentively. "Lay on your oars, men," ordered the sub.