LSGG Approach RWY23

[fdgolf]

Hello;
On Geneva's RWY23 ILS and VOR Jeppesen approach charts, there is a shaded area some 4 miles ahead and behind PETAL point. Does anyone know what it means?
Thanks in advance :ok:

[underread east]

If you are referring to the dotted line - following it south, it says it is the Swiss/French border which mostly runs through the centre of Lac Leman, encircling Geneva at the southern end of the lake. Nothing more exciting than that. If you are referring to the blue bit. That is said lake!