[MARCIANUS libro tertio institutionum. ] §1.8.4.prNemo igitur ad litus maris accedere prohibetur piscandi causa, dum tamen uillis et aedificiis et monumentis abstineatur, quia non sunt iuris gentium sicut et mare: idque et diuus Pius piscatoribus Formianis et Capenatis rescripsit.
[MARCIANUS, Institutes, book 3.] Therefore, no one is prohibited from approaching the seashore for the purpose of fishing, provided however that they keep away from villas, buildings, and monuments, because these are not subject to the law of nations as the sea is: and this is what the deified Pius replied by rescript to the fishermen of Formiae and Capena.
§1.8.4.1Sed flumina paene omnia et portus publica sunt.
But almost all rivers and ports are public.