Ingredients list is compulsory in UK, but water doesnt need to be listed. So the mince above is only allowed to be beef/pork/whatever you’re not allowed to advertise it as beef mince if there’s anything else in it, but they don’t have to state how much they’ve pumped it up with water.
Having said that beef doesn’t retain water like chicken and pork does, it’s the latter two that are most commonly injected with water. Not sure what the science is on that as to why.