More about Return from the Sea
There is no ocean in Return from the Sea...
There may not be a physical ocean but her gorgeous deep blue eyes are perfectly matched to the silky dress that is treatening to fall off her other shoulder. Luckily, Vallotton was part of a group of painters who only painted naked ladies when it made sense. This would've been a gratuitous nip-slip with Eugéne Delacroix or Guido Reni for sure.
In every description I've come across regarding this painting the woman is described as icy, frigid, or pissed off. I'm fairly certain she's none of these things and was asked by Vallotton to look straight at him and a neutral face is easier to maintain for a few hours than a forced smile. To me it looks like someone interrupted her reading and she's patiently waiting for them to finish their story. This is what happens when artists don't tell the world what they were trying to achieve and when art nuts mix their uppers and downers.
Though he often used his wife Gabrielle as a model this particular lady is unknown.
This was painted a year before Vallotton died, most likely due to complications from a botched surgery.