By the Late [Roman] Republic, the general idea of res communes was already well known in Roman culture. Plautus’ comic play Rudens, thought to date from c.190 B.C., features a fisherman (his occupation is important!) proclaiming that “the sea is unquestionably common to all persons” (mare quidem commune certost omnibus) in a longer speech that emphasizes fish as belonging to their captor.... [T]he concept becomes much more familiar in Latin sources from the Late Republic and Early Empire. Forms of common property are most often the air and the sea, but Cicero adds in the seashore (litus) as well. Although the familiar idea of common property was further elaborated in Early Imperial poetic or Stoic theories on the origin and development of human culture, there is no sign that these theories had any pronounced influence on the law; certainly they lead to no demonstrable legal conclusions.
By the Late Republic, a second cultural element had emerged: a widespread and often expressed disquiet about the startling proliferation of villas along the coast of central Italy and the Bay of Naples.... The architects of these villas, capitalizing on recently-discovered hydraulic concrete, often put down substructures extending beyond the shore and out into the sea — a phenomenon quite commonly referred to in legal texts, and one of particular concern to poets such as Horace who perceived the structures as morally hubristic. More exciting, however, is the discovery that not a few of the maritime villas incorporate fishponds so large that they were plainly intended to produce fresh fish not just for the villa, but for local markets.... [T]hese fishponds may well have brought the villa-owners into direct confrontation with more humble local fishers.