Most websites discussing the beaches around Rethymnon offer little prospect for naturist activity on this side of Crete. Indeed, the coastline for some 7-8km eastwards from the town is heavily built-up with hotels etc., many of which organise their own section of beach. Sadly, I found it universally textile.
However, there is one small section of beach which does appear to attract a few naturists. Follow the coastal road eastwards (not the main E75) from Rethymnon through Adelianos Kampos until reaching the end of the built-up area. This is actually the boundary between Adelianos Kampos and the next district and is marked by a road sign and bridge over a small (dry) river.
About 100m eastwards from the road sign and bridge, turn left onto a rough patch of ground used as a car park. If walking from one of the hotels in Adelianos Kampos, there is a pavement right along the road level with this same car park so traffic safety is not too much of an issue.
Once in the car park, follow the rough path towards the beach. Upon reaching the sand dune area, either head onto the beach turn right and walk along it or alternatively, turn right and follow one of the paths through the dune area. There is a small headland which separates the section of beach in question from the main beach. It contains an abandoned single-storey concrete structure and is backed by fields. The beach itself is mainly sandy with some pebbles and a rocky shoreline in places. However, it is reasonably well hidden from the main beach with few people passing along.
Upon arrival, I found two male nudists so I joined them for around an hour. In that time, a clothed couple appeared at the western end of the beach and did not seem fazed by the sight of naturists. However, when another group of textiles appeared from the main beach, including two children, one man put shorts on and the rest of us left.