A 120 minutes drive.
In the harbourfront of Chóra Sfakión there are a lot of tavernas and some rooms for rent. Besides the boat that will take you to Agia Roumeli, Loutró, Sougia and Paleochora, there is also a ferry that sets sail for the island of Gavdos a couple of times a week (two hours trip, usually in the weekends).
Just a half an hour walk westwards is the beach of Glykanera. You can walk on to Loutro but be sure to have good shoes.
Source: http://www.chora-sfakion.com/