In France, the historiography (1941–2012) of teaching swimming in physical education (PE) shows that there are dominant methods both in formal curriculum and in the professional world on the subject. This teaching is marked by two main methods: one based on an instrumented instruction to learn breaststroke, and the other based on the acquisition of swimming variations. These methods are needed for historical, educational, and axiological reasons. They became popular in PE while others continued to be rejected by the legislature and unknown to teachers. If the natural teaching of Raymond Siener based on natural flotation and fusiform posture emerges under the Vichy Regime (1940–1944), it does not become part of the formal curriculum until 1967 and remains little-known among teachers unlike the evolutionary and hegemonic concept of Raymond Catteau (1950–2008). This study is based on a corpus including official texts, teachers’ testimonies (144), works, and articles on swimming and shows that Raymond Siener’s method was rejected by the legislature for nearly 30 years and remained unknown to PE teachers for multiple reasons, in particular Siener’s own status, the “modernity” of this method, and its limited safety dimension.