Regardless of the water level and any motion, a narrowboat is always going to be sensitive to the effects of loading - and that includes someone walking around. It can be slightly unnerving to find that the boat lists slightly one way, and then the other, and when walking around (in heels or not) one can feel as though slightly drunk! Also, as I well recall when doing some work on my brother's narrowboat in fitting a shelf along one side wall, being pleased that my spirit level initially 'proved' the shelf was level - and then a re-check ten minutes later said otherwise! I simply forgot that the lack of stable foundations made use of a spirit level (or a plumbline) pretty well pointless!
