Stretching improves muscle flexibility and joint mobility and this is exactly what I do for at least 3 days per week and 30 minutes a day!
I breathe up gently for 2:00 through the nose, I exhale half of the air in my lungs and then hold my breath for 30sec while leaning on each side based on the same-arm-same-leg principle. I repeat 5 times each side increasing by 10sec each breath hold during every rep.
I know it might seem extremely boring, but this is actually a very nice and extremely beneficial stretching routine in order to improve freediving and spearfishing performance. This way I stay in good form and feel comfortable into the water any time I choose to freedive or spear.
Make sure that you are stretching correctly in order to prevent injury. Stretching is a great way to take a break from your busy day to recharge and strengthen your body and mind.