General tourist info: www.crikvenica.net

Crikvenica is situated in the Kvarner Bay, 35 kilometers south from Rijeka. The whole town of Crikvenica is in fact a riviera with a series of almost connected tourist places: Selce, Crikvenica, Dramalj and Jadranovo.

Nude beach is located near Kacjak tourist settlement, about 2 km walk along the seaside from Crikvenica.
If you're driving, turn left in Dramalj toward Kacjak, at the intersection with a market.
After some 500m first nude beaches start. If you walk (or drive) further toward Kacjak camping, after official FKK beach which is marked so and mostly visited by hetero crowd, you will found some places at the stony coast where you can swim and suntan naked. Parking is available near the official FKK beach.
This place is often visited by gay men especially in the afternoon and early evening. Those visiting in the evening are probably not there for swimming and sunning.

Thanks Tom&Maxon for additional Kacjak beach photos below:

Selce is a small town situated 3 km southeast of Crikvenica with well-preserved Primorje style, offering a number of visitor opportunities (hotels, campsites, rooms), with well-maintained, mostly pebble beaches; boat piers and small ports and a picturesque seaside promenade (Lungomare).

Selce has a quiet nude beach located near camping site Selce in area called Jasenova.
When you reach the camping and the coastline you have to turn left. After the shop there are three stairs where you have to go up. On the left side you will notice tennis courts. Following the path, after some 10-15 minutes of walking you will reach a nice beach.
First part of the beach is usually occupied by straight couples and after that area more popular among gays starts. It has nice flat rocks with good entrances to the water. This is also a good spot for those who like to just jump in to the water.
The beach is not very busy as it is not so known as some other beaches, and it doesn't have the reputation of "gay exclusively" beach, but there were nice reports about this beach so it is a worth of trying especially for those who seek some quiet and want to escape from busy textile Selce and Crikvenica beaches.
Above the beach there is a forest. The busiest days are of course during weekend.
In the water there are some sea urchins, but don't worry, this is a sign that water there is very clean as sea urchins live only in the cleanest waters.

Tourist association of Selce web site.