What’s the difference?

Recently I saw a post on here about a woman who was in her bathtub and she was wearing a tampon because she’s on her period. However, A LOT of comments said not to do it and I’m wondering what’s the difference of wearing a tampon in a pool than in the bathtub? You’re in water so why not wear it in the tub like you would a pool? I have never worn tampons, only pads and pantyliners so I’m curious to know why. Also, I’m asking here and not in the comments because I didn’t want anyone to think I was being smart.