Hi from Paris,
I have been often searching Geneva State archives for persons crossing illegally the border from 1942 to 1944 : last October, I copied there 250 files of persons linked to French Arbeter Ring / Workmen Circle, including my mother who was 13'.
Obviously, the easiest area to cross from Swiss to France was on southern part of Geneva Lake where border is just a line in middle of a field, specially in 1938 when France wasn't at war. I took some pictures near Annemasse, I could send privately to you.
I attach a 1942 map of Swiss custom / police stations in this area : in middle of map, lake's waters are colored in blue.
Mrs Ruth Fivaz, a Swiss historian, became History Doctor two years ago with her thesis " the flight to Swiss : migrations, strategies, flight, ... and fate of Jewish refugees from France during WWII".
I am sure she could be the "specialist" able to give some clues to you.
Archives and history of Medem Center, i.e. French (Bund) Arbeter Ring / Workmen Circle