It’s a long and tight latex (hobble?) dress. Even if you stand still you will feel the silky smooth latex with your whole body. When you walk, with every step your legs will overcome elastic resistance of the tightly hugging rubber grip. Very gentle and soft, but very noticeable bondage.
And moreover, transparent latex will hide neither bulge nor full size erection. But just in case your arms will be bound behind your back. Why to destroy such a nice view?
See also:
Erection of the day
Transparent rubber tights and catsuits
Latex on eBay – interesting finds
BTW, she looks like Emma Watson 😉