I took 2 days to kayak from Naramata to Rattlesnake Island then back to Penticton. Took less then 10 hrs. actual paddle time.
Total flat distance: 56.8 km
Total real distance: 60.9 km
Climbing distance: 17.4 km
Descent distance: 17.8 km
Flat distance: 25.7 km
Average speed 6.8kmh
More info and my GPX with waypoints and track is posted on my GROUP at:
Leave Naramata and head to these coordinates N49 44.879 W119 43.022 it's a fairly short kayak in a straight line but you will want to paddle mostly along the shore.