The rule of the river is to keep right, but just before we reached Worcester, I saw some navigation buoys in the water. These were green and triangular and sitting in the middle of the river. The rule, going upstream, is "keep the green floaty things on the right" (a variation on a notice we saw in Abingdon). It didn't feel like the right thing to do on this left-hand corner, but the buoys weren't there by accident. I reduced speed a little, just in case, but everything worked as it should.