Tom Fromm writes:
30. DIVE THRU: Starting formation - facing couples (man and lady). The couple whose back is to the center of the square (unless a specific couple is directed) makes an arch by raising their joined inside hands. The other couple ducks under the arch and moves forward. The couple making the arch moves forward and does a California twirl. If neither couple has its back to the center of the set, then one couple must be directed to dive thru the other couple.
STYLING: The couple making the arch uses a loose handhold. Stand far enough apart to allow another couple to dive under. It is permissible for dancers making the arch to part hands momentarily if it is uncomfortable to reach over diving dancers. After hands are rejoined, styling should be the same as previously described for California twirl. Couple diving under uses couple handhold. Bend low enough and stay close enough to partner to move comfortably underneath the arch.
TIMING: Box, couple diving, 2 steps; couple facing out, 6.
When teaching this move, I will tell them that we are going to learn a new move. I'll tell them the name of the move, and read them the definition.
I will walk them through a few times, telling the centers to make an arch, and the others "dive" through. I tell the ones that made the arch, to do a california twirl. For a few times, I will remind the ones that made the arch, to do that california twirl. I will tell them that they may need to temporarily drop the arch, to allow taller dancers to get under.
To start with, I will only use dive thru from an eight chain thru starting position. Also, I will only have the centers make the arch. Later, I will show them that we can do it from facing lines, but that I have to specify who does the diving. I will also have them in eight chain thru, and designate the centers to do the diving. Many will say these later uses, I want to at least show it to them. I found that when teaching a class with no angels, this use went very well. It was at their first dance with existing dancers, that we ran into problems, and had to refrain from using them.