Asimov and others have been saying that no work is being done because no distance is moved, but is that no the same for the stationary boat using 1000hp to maintain equilibrium. So clearly you have to take your distance with relation to the water not the actual position in space. Meaning as the anchor is providing a force and is going a distance (relative to the water as previously explained) it is doing work. as the speed of the river in both cases is the same, i would say it would be doing 1000hp of work, but i cannot work out where this energy is comign from, in the engine example it is comign from the fuel, here i dont get it, is it e.p.e or strain energy or somthign, but that doesn't make sence as thats liek a gain of energy with regards to the system which is impossible. It is a rather confusing senario, but i dont think you can say as it isn't moving no work is bing done, as this would be the same for the motorised boat but we have been told it is doing work.