Pedersoli returned to Italy in 1949 to play water polo in Rome for Società Sportiva Lazio Nuoto and won the Italian swimming championships in freestyle and mixed relay teams. As a professional swimmer in his youth, Spencer was the first Italian to swim the 100 m freestyle in less than one minute when on 19 September 1950 he swam the distance in 59.5 s in Salsomaggiore. In 1949 he made his international debut and a year later he was called up for the European championships in Vienna where he swam in two finals, finishing fifth in the 100 m and fourth in the relay 4 × 200 m.