Flat to choppy water, depending on the wind strenght. Very small sandy beach, not much space. Can get packed with people, then it is recommended not to launch. Nice weather in summer, too cold in winter. Wetsuit in spring and fall.
If it is not good try that spot: http://www.kitesurfmaniac.com/switzerland/la-plage-19.html
How to go there
Lac De Neuchatel (Neuenburger See). Exit A1 at Yverdon, turn right towards Yvonand for about 10km. Then follow the signs to Refuge