School of Yoga explains Makarasana – Crocodile Pose

Makarasana technique:

Sthithi (starting pose) – Lie down on your stomach, face down.
Bring the elbows under the shoulder and lift the upper torso such that the elbows are together and the face is cupped in the palm of the hands.
Fold the knees backward such that the heel rest on the buttocks.
Keep the feet and knees together; relax the muscles in the back and abdomen.
Maintain shallow breathing. Maintain position for 10 counts.
Inhale and return slowly to sthithi (starting) position. As you return, feel the vertebrae returning to correct position. Get the hands back to the sides.
Breathe normally. Repeat 3 to 6 times.
The drishti (gaze) recommended is Oordhva drishti (open sky gaze).

The stretching action energises and strengthens the muscles of the back with increased blood supply and makes them supple, elastic and flexible.
The spinal chord and cartilages get rejuvenated for the same reason. This exercise is very good for retaining the arch of the spine and prevents backache. Tones up the sympathetic nervous system.
This asana is a very good beginners asana.