Surfing is a sport for the whole body, using different parts in combination and in sequence. You should train for it in the same way, creating a circuit.
Flexibility is achieved through stretching exercises.
Paddling requires strength: do lateral raises and straight-arm exercises, focusing on the lats. Work your triceps with dumbbell exercises.
Circles make your shoulder joints more flexible.
Develop strength in arms and chest with burpees and lizards allowing quick pop-up.
The core strength improves with abs exercises.
You can add the cobra posture of yoga.
Leg strength comes with lunges.
Observe your breathing during exercise, it must accompany the movement, without interrupting it.
Work out a few times a week and you will be in the best shape to surf when it’s time to hit the waves.