Austria' s biggest inland lake can be found near Salzburg, the lake "Attersee". This lake is really a paradise for divers. All around the lake there are a lot of access for divers with very nice dive sides.
In Weyregg at the east coast of the lake you can find the dive base "divesport". A very good place to make your course or just for lending tanks.
Unfortunately the weather was not really like it should be at the end of July, but the experiences under water were anyway fascinating.