They are wearing Speedo brand briefs.
The Speedo logo is on the left hip.
American Speedo briefs seem to have the Speedo logo on the right hip.
European Speedo briefs have the Speedo logo on the left hip.
It would appear that they are wearing European Speedo brand briefs.
Speedo UK do not have a royal blue brief.
This is the closest that I can find:
https://www.amazon.co.uk/Speedo-Logo...Z2Y9 BJ9QCK8G
I suspect it comes from Germany.
I suspect the front seam is an optical illusion
Speedo Australia have left hip logos and royal blue briefs:
https://speedo.com.au/product/men-s-...ief#12073/1725