Simply shoot into still water and adjust nock height and rest so you make the least amount of splash on entrance or find a soft dirt bank or mound of sand and shoot into it and adjust accordingly for nock high/low and in/out. You can also achieve better tuning if needed by cutting the length of the fiberglass arrow, in effect increasing spine, or adjusting the weight of the barbed point. Heavier point will decrease spine, lighter head will increase stiffness. You're on the right track to tune the bow as your arrow will penetrate the water better with less deflection and will penetrate large fish better as well.