There is a lot of information circling around the importance of being flexible, but it needs to be put into the context of the activity or sport. How much do we need and where? And is it a priority for successful surfing?
In my experience with beginners learning to get to their feet, the biggest limitation they face is lack of strength, then co-ordination, rather than a lack of flexibility.
Exercise physiologists will explain to you that muscles work in opposing pairs, while one side contracts to cause movement, the opposing muscle needs to relax and stretch to allow this to happen. So the range of movement is one issue, the speed is the other.
Getting to your feet from a lying position requires a co-ordinated effort between shoulders and hips. The range of movement is no greater than most movements we already perform! eg, we dont need to touch our toes... We are not moving through an extreme range of movement at either of these joints, so flexibility is not as important as having strength in the muscles around the shoulders and the legs.
So, it is far more critical to improve strength and ultimately power (thats another story), by performing exercises that take you through a full range of movement, thereby requiring those opposing muscles to be stretched WHILE you strengthen.
My final word on this matter....good flexibility will not get you to your feet quickly!!!