It's not even screwed in. You just twist that bit (which twisted pretty easily on mine) and the battery pops out. I dread to think how often this has been floating round the bath while DC are in there. It's not the smallest button cell but still. Pretty sure it could still be ingested or at the very least, a choking hazard. I always watch DC while they're in the bath but that battery could have popped out and been in either of their mouths within seconds!