Butt excercises required for "tunneling"

[Torchwatch]

If you stand with your legs straight and your knees locked, your ankles together and your feet pointing outwards, and your hips forward and locked; you will find that you can hold a credit card between your buttocks. This is the wrong posture for tunnelling, you need something more fluid and relaxed.
Move your feet apart and point them inwards, bend your knees, unlock your hips and let them slide back a bit, and arch your back. You are now in a Tai Chi position in which you feel relaxed and can react to any attack, but looking in the mirror you should present a nice tunnel.
Any exercises that slims your waist and muscles your abdomen will improve your appearance, the arched back moving down into the rounded bottom gives a sensous effect (if the waist is slim), especially in low cut speedos.