Lol...nice one pepe.
In austria I mainly use my drysuit since temperatures are pretty low in mountain-area lakes. Especially if you go below about 15m.
Green lake is pretty shallow, it was about 7-8m, the depth depends very much on how much snow is melting in the surrounding area as it gets filled up by it.
Hope you get into diving Hans, it can be really relaxing at times cuz its just so peacefull and quiet down there. From time to time I just pick an underwater spot and sit around there, watching fish and listening to my own breathing and nothing else
Edit: and dont hurry too much in taking a camera with you, make sure you are good at diving first before you occupy your hands too much underwater. Otherwise you'll start rising and dropping all the time.