Speedo Questions
 

Some speedos have a thin mesh line at the back, specifically the crack area

Why is it there, what does it do and what do you call it?

Pics here https://malaysia.answers.yahoo.com/q...5073111AA9fdxn

Also here https://www.youtube.com/watch?v=Yv1X...62D2&index= 1 @ 1:16

These are common in swim briefs destined for the asian market. Supposedly the mesh drains any water that accumulates inside the brief while swimming. The Aqux-branded briefs I imported all have this feature. Also, the briefs with the mesh often fit really low in back, leaving the top part of the butt-crack showing. The mesh seam can be made to cinch up between the glutes, dividing them, but also leaving a bit less butt crack showing. The seam fits between the glutes almost like a thong. The whole idea seems to be part of current asian style, very low riding in back showing a little butt crack with the mesh seam riding tight between the glutes.