A Video Not In Favor Of Speedos ........... However
 

Read all the comments that are in favor of them: :D

https://www.youtube.com/watch?v=N9xr_mJc5cg

I'm confused, 5 of the men posing in "unsuitable swimwear" were wearing underwear and the guy in Speedos was clearly wearing Adidas swim briefs.
Yes white cotton underwear goes transparent when you swim in it but do you really need a warning on the packet ? Don't put cups of hot tea between your thighs when driving, don't stand on toilet seats!
The guys in this video were body builders and some of them wore body builder posing suits, is this a surprise? Body builder posing suits are intended for posing, not swimming and sunbathing, so the video ends up showing only 2 real swimsuits one of which is wrongly described. Many body builders wouldn't pose naked as it would show up all the steroid injection marks (usually hidden) on their butts.
The video is just an excuse to show a bunch of oversized bodybuilders by the pool and on beaches and has very little to do with swimming or swimwear. And conclusions you may come to about men's swimwear would be bogus

RE:Swimwear
 

Agree with the above poster.
Underwear is definitely not appropriate swimwear, nor is a thong in most places.
Tangas and posing suits are pushing the limits.
To include speedos, swim briefs and square cuts, all of which are perfectly legitimate swimwear with them makes no sense.