I'm a little bit late to the party on this, but many people still don't know about it. Since they added the 2nd layer people have been using it to add and change things, this is like that but you can take off your clothes as they're in the 2nd layer. Simply go into Options>Skin Customization and then toggle what you off, toggling the legs gives you swim trunks and toggling the jacket and arms makes you shirtless.

TL:DR unless you don't know what this is