Plaja Gostinu
Plaja Gostinu is a little different from the other beaches on the list because it's not on the Black Sea; instead, it's on the banks of the famous Danube River. Apart from the lack of crowds, the advantage of visiting this beach is that it is relatively close to the capital, Bucharest, so you can simply take a city break and drive out for a few hours of sun and sand. In those busy days and need to relax, it's great that you can drive here and enjoy wonderful relaxing moments.
The beach isn't particularly wide, but it'll never be overcrowded, since most people prefer to head to the coast and enjoy the Black Sea beaches. They're losing out, though, because this is a wonderfully gorgeous and relaxing spot that's perfect for nature enthusiasts. If you're a bird watcher, bring your binoculars because there are plenty of places to see birds while taking a dip in the calm waters.