Jun 17, 2018 - 11:14 PM
Just go from Wengen down to Interlaken on the WAB/BOB railways.
Interlaken has two railway stations Ost and West. Ost is the railway interchange between ZB (Luzern); BOB (towards Jungfrau) and SBB (main line) trains. West is the town centre station, and has bus and boat interchange:
Boats to Brienz depart from near Interlaken Ost, boats to Thun depart from near Interlaken West. In both cases you can do one way by boat one way by train (helps keep the length of the excursion manageable.