Flip Breskin of Bellingham, Washington taught me to sing it backwards:

Dream is but a life
Merrily, merrily, merrily, merrily
Stream the down gently
Boat your row, row, row

You sing the melody backwards, too. That is, each syllable has the same pitch as it does in the original song, although the meter follows the words. (On the last line, for example, "Boat your" is a dotted eighth-sixteenth on the fourth beat of the measure, and "row, row, row" are four quarter notes on the first 3 beats, ending with a quarter rest. Get it?)

Aloha,
Mark