Hello benjaminfrombedminster,
This article details the different types of workouts available for the Apple Watch: Workout types on Apple Watch - Apple Support. While there is no specific paddling workout, there is rowing and swimming. Either of those may track your paddling activities as you wish.
You can also create a workout:
"You can browse and add new workout types to the Workout app.
- On your Apple Watch, open the Workout app.
- Scroll down and tap Add Workout.
- Tap the desired workout.
Choose Other when you can't find a matching workout type. In all workouts, the Heart Rate and Motion sensors work together to give you accurate credit. When you use Other, or any workout type available in the Add Workout section, you earn the credit equivalent of a brisk walk when these sensor readings are unavailable.
Learn how to get accurate measurements using your Apple Watch to make sure that you're earning the most from your workout."
We hope this helps. Let us know if we can assist with anything else at all. Take care.