vrh ledenog brega

1. the tip of the iceberg
   Ovi slučajevi su samo vrh ledenog brega. — These cases are just the tip of the iceberg.
   Afera o kojoj pišu novine samo je vrh ledenog brega. — The scandal the papers are writing about is only the tip of the iceberg.

Usually used with samo: to je samo vrh ledenog brega, "that's just the tip of the iceberg".