While also rare, spinal injuries can occur while surf jumping and, potentially, wake jumping. The PWC manufacturers owner's manuals all include warnings regarding jumping at excessive heights, or operating a PWC if there is a prior history of back injury. The current on-product labels say "Jumping wakes or waves can increase the risk of spinal/backbone injuries (paralysis)". The current Kawasaki owner's manual provides: "Slow down before crossing waves. Do not ride if you have a back condition. High speed operation in choppy or rough water may cause back injuries."