Towed by the two steamboats of the _Simplicita_, four cutters from the _Paradox_, _Eureka_, and the seaplane parent ship set off up the river. Into the boats were packed one hundred and twenty officers and men drawn from each vessel of the little squadron. Each boat carried a quick-firer in the bows and a Maxim, in addition to stores sufficient to last a week or ten days. The expedition was under the orders of Lieutenant-commander Bourne, while amongst the officers was Sub-lieutenant Frank Denbigh, with Armstrong in charge of stores. Much to his disgust Pat O'Hara found himself "turned down" by the Principal Medical Officer; the former's assurances that his ankle would improve with a little exercise being brushed aside by the latter, who knew perfectly well that days would elapse before the Irishman could set foot upon the _Crustacean's_ deck, let alone the crowded stern-sheets of an armed cutter. Before the boats were out of sight of the still stranded _Crustacean_ two sea-planes ascended and flew swiftly inland. Without their aid the landing-party would be literally groping for their foes, since it was not known whether von Riesser and his men had taken to their boats or had set out through the mangroves towards the grass-grown hinterland. Denbigh having more knowledge of the Mohoro River than any of the other officers--and his knowledge was limited to a stretch of less than ten miles--was navigating officer in charge of the leading steamboat. While the other officers were sweeping the mudflat fringed banks with their glasses Denbigh directed his attention towards the turgid channel. Presently a line of bobbing objects caught his vision. Ordering the leading stoker to ease down the engines he signalled by means of hand-flags to the steamboat astern to likewise reduce speed. The objects that had attracted his attention were the barrels forming the boom across the river almost abreast of the wrecked torpedo-station. The _Pelikan_, he knew, had been moored above the obstruction. She had drifted down past them before she took fire and blew up. Unless the boom had been temporarily removed and afterwards replaced he could not understand how the raider could have descended with the ebb-tide without sweeping the line of barrels away. "What's wrong?" enquired Bourne. Briefly Denbigh explained. "It would be as well if we sent a shell into one of those barrels," he added. "Waste of good ammunition," objected the lieutenant-commander. "The steamboat can take it bows on at full speed ahead. She'll do it easily." "That I do not doubt," replied the sub. "But I have an idea that those barricoes are filled with explosives, although we bumped into one of them when we were in a light punt."