God thats shocking fortunetely I have dd's so that doesnt count but dh wears shorts with the inner lining in them. I will pass on the information and it will be just another reason for him to hate swimming.
Oh god - that happend to my DS (age 3) when we went swimming. Wasn't sure what had happened at the time but later realised - it wasn't too serious but there was a lot of blood and he couldn't wee without screaming in pain for a couple of days.
This happened to my friends ds when we went on holiday with them. He must have been about 7 at the time and all the mums ended up crowding around as his foreskin swelled like a baloon, trying to free him from the mesh. I had a small first aid kit in my bag and remember trying to cut the mesh away with a pair of nail scissors without cutting his skin! We all panicked a bit tbh.
I had forgotoon about this but have never got my ds any shorts with mesh, only swiming trunks.
As the adult ones have these as well I think a poo catcher is unlikely. I think they are fall catching other 'objects' that may fall out . Although for small kids I think such fallout would be unusual - perhaps it's just so that they can be like Dad?