The American brand may not even be available in England but that hasn't stopped them from amassing a loyal fan base over here.
Though it's not because us Brits just love to keep hydrated.
No, 138 rely on skimpily clad models to drum up attention and their latest campaign is no exception.
Canadian Model Cate Chant shows off her smoking hot bodyDressed in a skimpy orange bikini, model Sammy Mitchell wows as she flaunts her petite frame on a sun-kissed Malibu beach.
In one shot the star can be seen seductively flipping her hair in the breeze while in another Sammy proudly pushes out her booty for extra sex appeal.
However, in a bizarre break of tradition, the brand have failed to get Sammy to pose with their trusty bottle of water.
Sam recently impressed the world when she came fourth in Swimsuit USA's International Model Search.
Speaking about the pageant, Sammy said: "After all the hard work and effort I have put in to this competition, I can excitingly announce I placed in the top five in the world and that hard work has definitely paid off.
"I couldn't have done this without my sponsors, mentors, family & friends."
Model Jessica Melody shows off her toned curves for 138 Water
Proving she isn't bitter about missing out on the top spot, she continued: "Congratulations to my pageant sister, Perth babe and roomie @cassy_walker for winning first place, I couldn't be more happier for someone who absolutely deserves it.
"To the runner ups and all the beautiful contestants who competed, you all did amazing and we are all winners in my eyes."