get a seat harness if you have a bad back, are really old, or think windsurfing is cool
otherwise get a waist harness
News flash windsurfing is cool. Like most people with that opinion you have probably never seen good winsurfers do their thing. If there is any kind of chop and solid wind a good windsurfer would leave you in his wake. And lets not forget those old windsurfing dudes with bad backs are the ones that created kitesurfing. Thank you Robbie , Pete and others...