Complex sentence: Unfortunately, the promise of making a fortune outweighs the threat the mermaid represents, and no one will listen to Lily's dire misgivings--that is, until the mermaid escapes her tank, and begins to eat the crew members, one by one.
Split into simpler sentences: Unfortunately, the promise of making a fortune outweighs the threat the mermaid represents. No one will listen to Lily's dire misgivings--that is, until the mermaid escapes her tank, and begins to eat the crew members, one by one.