Lower back pain from surfing

I know that this is common, especially for newer surfers like myself. I’m fairly certain that my constant lower back soreness is from overarching while paddling and catching a wave. For those who are much more experienced out there, do you have any solid suggestions for effective stretches, along with core and upper body strengthening exercises so that I can stop straining my lower back muscles so much? Or critiquing of ways I could change my positioning and technique while out in the water? Any and all advice is appreciated. Thank you!