Downwinding Between Flüelen & Beckenried
Switzerland has many large lakes that can generate favorable conditions for downwind runs. But pay attention to weather forecasts and water temperatures just as you should anywhere if you want to paddle safely. Watch this 2019 sailing race video where an epic storm comes up on Lake Geneva with 60 knot winds.
Nernier to Anieres (downwind with a 'Bise' which is a regular NE wind)
Lakes known for their turquoise waters surfski video
Gersau - Meggen
Swiss Marathon Paddle Cup SUP, Outrigger, Kayak (Surfski not specifically mentioned, but if not yet included it's only a matter of time until they do)