Novoland: Pearl Eclipse Episode 22

While in Hai Shi's village, assassins take Hai Shi's mother captive to force her to sign a document that Fang Zhu is colluding with the leader of the Left Huku Tribe, who looks like Zhuo Ying. Fang Zhu and Hai Shi fall into the water, where they meet the mermaid who helped Hai Shi as a child. A captured assassin claims he's working for Lord Chang, so the Emperor and Fang Zhu put them through a test. Fang Zhu cautions Zhe Liu that her new role in leading the spy network will put her in danger. (Source: frankly at MyDramalist)