Adding to Ewan's fragment (perhaps erroneously)
There's tug boats and row boats and all kinds of craft
Boats with no engines and boats with no draft

A double canoe is perfect for two
When messing about on the river

There's XXXXXX backwaters hidden from view,
And XXXX little islands just waiting for you,

In the summer of 1995, a group of West of Scotland singers put on a tribute to Josh McCrae in Glasgow's Tron Theater - the late Danny Kyle was MC, and on stage, singing Messing about on the river, if I remember rightly, was Josh McCrae's daughter. Maybe Ewan can confirm. My mind is fuzzy, because the Glasgow Socialist Women's Choir and a pickled Mick Broderick then took over in the bar, and the night went merrily to hell... The point is, the song seemed very much alive and well, and half the theatre audience sung fragments.