Hi, Theseus
You probably found in proz the translation
η κορυφή του παγόβουνου for this one and found in Lexilogia this
iceberg thread.
However, I'm not sure that the proposed translation in proz could be used in the case of your example, as this one shows fear for something that could be in the making, not of something existing (just not visible).
I think, in the case of your example, it would be better to leave icebergs aside and try for other phrases, starting with [...] μπορεί να
είναι μόνο η αρχή. Another idea is
άρχισαν τα όργανα, e.g. Με τις ταυτότητες για τους φιλάθλους άρχισαν τα όργανα... (musical instruments, that is).