Particularly worth noting are three cruises of the Icebreaker Sadko, which went farther north than most; in 1935 and 1936 the last unexplored areas in the northern Kara Sea were examined and small and elusive Ushakov Island was discovered.
Particularmente dignos de mención son tres cruceiros do quebraxeos Sadko, que pasaron máis ao norte que a maioría; en 1935 e 1936 as últimas zonas inexploradas no norte do mar de Kara foron examinadas e a pequena e recóndita illa Ushakov foi descuberta.