There are some issues in the world of Law that appear more as dogmas than as a result of normative analysis. The topic of the public legal nature regarding the beaches of rivers and lakes, is one of them. In this work I will try to determine it by carrying out a systematic review of its scattered regulation and the scarce jurisprudence that pronounces on them, contradicting the brief arguments that usually are used to justify their public nature. In the case of lakes, I will propose a position that questions the classic theory because, as I will say, there are no such things as public beaches in Chile. Finally, I will explain the eventual publishing consequence of the declaration of navigability of a lake, and how it could be considered expropriatory.