Of course anything new is scary hopefully they will eventually warm up to it. maybe your friends can get in it while the water is poop free and show them it's fun. lolMy friends have gotten the geese a kiddie pool and are feeding them fresh vegetables. My hunch is that your suspicion of hardware disease or something similar is probably correct. They have already tried antibiotics and have had the only qualified vet in our town out several times, so I don't think there's much more they can do at this point other than try and improve his quality of life. They said that the geese are afraid of the pool, though, and won't go in it!
Too bad if it is hardware disease. I go over my property at least 1X a week and find nails screws staples it's amazing what the rain washes up. I bought a magnet on a long handle works great.