Its also recorded on an early Peter Bellamy LP - Fair Englands Shore - as 'Prentice Boy' I think. Its a bit different to the lyrics here and in Malcom's link, both in words and structure, but not that much. I expect it'll be the Harry Cox version, and it has these lines in diffrent verses..

A'floating by the river bank that that flows through Ekefield town

That flows so brisk and narrow, that flows so deep and wide...