hi doc! i m a police officer assigned on a special boat unit.. we patrol coastal waters on a small water craft known as inflatable rigid hull boats.. everything s fine except that lately i ve been noticing persistent pain on my lower back just above my butt area.. i suspect that it might be have caused by the boat ride, coz when we cruise at high speed at est. 35-40 knots, the sea got really bumpy (and those who have tried jetski will say it is really hard,bumpy ride). the bumpy ride shakes everyone inside the boat... my question is, is there any injury? additional: if i would stretch my side and back area, i could feel and hear cracking sounds.... thank you so much...