Tug or a shove?

Still diverted by the coast. Saw a tug shoving a barge up the river this morning. Always thought of a Tug as tugging or pulling, never really shoving or pushing. Mind you with a name like 'Bruiser' I suppose it could do either. The very low tide made the tug look like it's plying through mud. A sprinkling of birds for some life on the grey day.