Yes, that was underwear and probably more of a thong in design (which I don't find comfortable but was enjoying the front view).
The brand is HOM Joe - as you will see in the pic and for which you should read posts #23 and #24.
HOM started in Marseilles with men's underwear in 1968 and later added speedos to their range. The brand now belongs to German conglomerate Triumph International (the girls will recognise Triumph as a long-time producer of their swimsuits).
You might care to have a look at
http://www.hom.com/en/sous-vetements-homme/histoire/
You can select English but if you come across French sous-vetements are underwear and maillots de bain are speedos.