This trip takes you to the natural wonder of Balos Beach, with its lagoon and surrounding islands. Phalasarna, with an archaeological site and a beautiful beach, is an extra option.
There are several options for this trip. There is an organized tour from Plakias to Balos Beach (Gramvousa), this does not include Phalasarna. You can go by car to Kissamos and take a cruise from there or drive straight to Balos Beach.
It is a long drive but absolutely worth it, although I recommend making a 2-day trip out of it with an overnight stay in the Chania/Kissamos region because Balos Beach is especially breath taking at sunrise or sunset when it's no too busy yet either.
You can also go by bus with bus changes in Rethymno and Chania, in which case I suggest an overnight stay in the region as well.