![The Little Mermaid mistake picture](/images/screenshots/366000-366999/366846_sm.jpg)
Revealing mistake: Ariel swims underwater and opens a book with stiff and easy-to-flip pages that produce a flutter sound when turned. The paper should be either soggy, or with its pages stuck together or even dissolved, and in no case sound and look as if it were dry.
Answer: Her long hair covered her up.
There are a couple of shots after her transformation where you can tell she's no longer wearing her bra. However, I rewatched her transformation scene, and her bra is never seen coming off. It's just gone.