How did the 3 men aggravate the people on steam launchers?

Basically they would find themselves in the way of the steam launch,

I can honestly say that our one small boat, during that week, caused more annoyance and delay and aggravation to the steam launches that we came across than all the other craft on the river put together. “Steam launch, coming!” one of us would cry out, on sighting the enemy in the distance; and, in an instant, everything was got ready to receive her. I would take the lines, and Harris and George would sit down beside me, all of us with our backs to the launch, and the boat would drift out quietly into mid-stream. On would come the launch, whistling, and on we would go, drifting. At about a hundred yards off, she would start whistling like mad, and the people would come and lean over the side, and roar at us; but we never heard them! Harris would be telling us an anecdote about his mother, and George and I would not have missed a word of it for worlds. Then that launch would give one final shriek of a whistle that would nearly burst the boiler, and she would reverse her engines, and blow off steam, and swing round and get aground; everyone on board of it would rush to the bow and yell at us. ch 13