If it were just a soft C, then "ocean" would sound more like "oh-see-in" or "oce-yin". But it's also been palatalized to sound like "oshin" in typical pronuncia

If it were just a soft C, then "ocean" would sound more like "oh-see-in" or "oce-yin". But it's also been palatalized to sound like "oshin" in typical pronunciation. People might not have understood them because they didn't know this.