Hi
When recording specific fitness activities, using the Workout app (or a third-party app) and choosing the activity type that most closely matches your workout - including choosing Other for workouts that are neither included within nor sufficiently similar to those in the main list - enables Apple Watch to use the most appropriate sensors and data sources when tracking results.
There is currently no option for tracking kayaking / canoeing with distance recorded and a tailored calorie calculation.
One option is to record your activity as an Open Water Swim workout. Distance would be tracked using the built-in GPS on Apple Watch Series 2 models and a route map recorded, but active calories would be estimated based on the assumption that you are swimming continuously.
Another option is to record the workout under "Other". For "Other" workouts, one minute of Exercise is credited for each full minute of the workout and active calories are estimated at a rate equivalent to a brisk walk or based on data recorded by the heart rate sensor, whichever is higher. However, neither distance nor a route map are recorded under this workout activity type. Upon saving the workout, it could be labelled as "paddling", though this would not affect the basis on which calories are estimated.
More information:
Work out with your Apple Watch - Apple Support
If you would like to submit a feature request to Apple (in respect of adding kayaking as a main workout type), then you can do so here:
https://www.apple.com/feedback/watch.html