Swiss Railways (SBB/CFF/FFS) operates a train from Geneva to Saint-Prex every 30 minutes. Tickets cost $22 - $40 and the journey takes 25 min.
How to get from Geneva to Saint-Prex
From Genève train to Morges then line 3 train to St-Prex. 50 min SFr 39. From Genève line 250 train to Allaman then line 4 train to St-Prex. 51 min SFr 35. From Genève-Mont-Blanc ferry to St-Prex CGN. 2 h 45 min SFr 45. From Geneva taxi to Saint-Prex. 34 min SFr 210. From Geneva drive to Saint-Prex. 34 min SFr 7.