There are two main reasons why it is important to do a surfing warm up. First your body works more efficiently with warm muscles and ligaments so your performance will actually improve. Second your body will be less prone to surf injuries.
You can do your warm up while watching a couple of sets roll in. This way you will be warmer, limber and more flexible. With a good surfing warm up you will maximize your surfing performance in the water from the first moment.
WARM UP BODY
Start with some gentle exercises to warm up the whole body. Increase your heart rate, breathing and blood supply to the muscles with some light jogging up and down the beach.
LIGHT MOBILITY EXERCISES
Add some light mobility exercises like arm swings, leg swings etc. Start with your head and neck and work your way down to your ankles. You can add some light stretches but real long stretching should be done after your session.
A good surfing warm up should be continuous and rhythmic in nature and last between 5-10 minutes.