triathlon nontraditional- If one were to set up a half triathlon what would the kakak distance be.?

I have this discussion with a buddy about doing a non swimming half ironman distance triathlon. It would have of course a 56 mile bike ride, 13.1 run but start off with a flat water kakak, instead of the 1.2 mile swim. What would be an equivalent distance to that swim? Has anybody done a tri with a canoe or kakak leg?