Stand beside the edge of the pool. Step on the noodle with your far leg (far from the edge). Hold the edge with straight arm. Keep your back straight and your far leg slightly in front of your body.
Straight leg raise as high as you can toward the surface. This is easy because noodle is pushing your foot toward the surface. Push the noodle down. It is very important to keep your leg straight. Here you will work against noodle's resistance. Make sure to push down as deep as you can until your leg is back to the starting position.
Inhale when you raise your leg up. Exhale when you push down.
Feel your hamstring muscle as you push the noodle down.