[Firebrand]

I would build it with increasing skill level mastery. For example, have them navigate to a Spanish Galeon with sunken treasure, and back to the anchor line. Then have them do it in a square pattern, with other interesting things to "see," and then go to the triangle. Provide hints for compass use while at the turning points.

After the students master the basic skills involved, make a more advanced navigation level where they have to swim against a cross current (change the direction they face, to swim along the desired azimuth) and so forth. I understand that the skill for this is usually aquired by feel and watching the bottom, but this could aid their understanding of the principles. Again, do this with the simple, out and back method, and move on to the different methods (box & triangle).

Once this level is mastered, create a practical experience where they combine all the skills and have to lead the diver to recover a cool item at the end of the challenge.

Don't forget to include the students counting their fin kick cycles!