Strangest thing.....
Yesterday my wife rings me at work and said there was a turtle on our front doorstep trying to climb the screen door! (It's bigger than a trackball mounting plate.)
I live in Sydney suburbia, lots of houses and roads. Nearest running water is probably 2 miles away and if it came from there it would had to successfully negotiate at least 4 major intersections and a bunch of kids on school holidays.
I have no idea where it come from or how it made it to our place! My wife asked around the neighborhood thinking it may have been a pet that escaped but nobody put their hand up.
It looks like its had a hard life as its shell is pretty smashed up but seems otherwise healthy and is very active. It's living in our bathtub at the moment.
I considered keeping it but will take it to a wildlife park not far from me today