A favorite at 19 months old! I only wish we had found this one sooner! Appropriate anytime between 1-2 years.
We sing the song and she loves to sway to the song and respond "Ah!" and "Rawr!" to the lyrics. I don't think that these lyrics are "official" but they sure are fun and add a new element of interaction to the song:

Row row row your boat, gently down the stream.
Merrily, merrily, merrily, merrily, life is but a dream.

Rock, rock, rock your boat, gently down the stream.
If you see a crocodile, don't forget to scream. "(Ah!)"

Row, row, row your boat, gently to the shore.
If you see a lion, don't forget to roar! "(roar!)"

The illustrations match the rhyme - the very thing for kids who want it read out loud again and again!