For my cardio workouts Apple Watch is fine. Today I went swimming (without the watch...) and afterwards added the activity manually to the Health App. The Health App shows the activity correctly (in Trainings and Activity Calories). But the calories and training time are not added up to the Activity app (one the watch and phone). So in the Activity app I only see the activities from walking around during this day. So it seems to me that it's not possible to add a workout manually to the activity app. Or am I doing something wrong?