We play underwater frisbee golf using one of the smaller reef systems triangles for a hole, each toss is a stroke, each time you touch bottom add a stroke, each time you hit the surface add a stroke. No skulling or finning allowed or strokes are added. Students keep tossing until the underwater torpedo
(which works better than the underwater frisbees) goes through the triangle. You can make this game VERY difficult if desired using the shallow end for your hole. You usually don't need the shallow end! Give away a tee shirt or class discount and watch em WANT to work on their buoyancy to win. It's a blast!
One other game the students for some reason like much better involves hitting the instructor with the torpedo, while both are hovering. Gee, i wonder why they like this one best? We usually give them 10 tosses, they must hover while tossing & lose tosses when they hit the bottom or top. Again give something away to the winner so it's worth the effort.
One other game we have talked about but not done is some form of underwater no-mask navigation, to help with the no mask breathing. Maybe blindfold & guide them so they don't get to far off the mark. Haven't figured out a safe way to do that one yet, but think it might be a helpful game.