Well, there's WHALEBOAT MALARKEY (Joseph Spence). And there is the song Skip Henderson sings, not immediately findable on DT, whose chorus goes:

I's the boy that built the boat,
I's the boy that sails her,
I's the boy to catch the fish,
and takes 'em home to Lisa.

Then the DT has an unusually literate version of "Our Lugger Venus," truly a song about a boat. And finally, I think I recall one that goes something like his:

Row, row, row your boat, gently down the stream,
Merilly, Merilly, Merilly, Merilly,
Merilly, Merilly, Merilly, Merilly,
Merilly, Merilly, Merilly, Merilly,
Merilly, Merilly, Merilly, Merilly (I forget the rest.)