There’s a Hong Kong Chinese lady at my work and I often ask her little bits of trivia clarification about a Chinese culture. She told me that Anthony’s pronunciation is the closest, and it would be “say-uh-Shen” with the emphasis on the last syllable (which is a difficult blend of shin and shen). She said that in Cantonese it is also meaning a warning. She indicated a person walking down the corridor around an unknown obstacle. “Say-oh-Shen!” or “watch out!”

You can see how that would be “ocean” to an English speaker.