I have added Volleyball as a custom app (even though it can not record it as the volleyball activity type, which is still not available, it records as Other Named Volleyball). But you can use it to score the game as well.
Volleyball is quite difficult to play with watch. When I used to play beach volley, just worn chest band and synchronized data afterwards. 2 hours of intensive beach volley were kinda more than run of 15 km.
