hey mark like most i only gave the pfd a cursory glance when throwing it in the boat. Then had a big shoulder injury and op. Previously loved swimming up and down the local beach missed that alot.got the pfd back on in rehab after long crappy period of therabands etc. flapping alomg breaststroke with one arm mainly was brilliant therapy .improved fast and went on to another type of floatie just around the waist and soon came good.my point is get it on and use it to swim say amile.you realise what agreat aid they are.you will no doubt improve on the design and i wish tou success regards wizza