"After the female successfully escaped ashore, the mermaid unfortunately could not leave with her." Fei Rui continued, "Because once they were on land, the mermaid no longer had an advantage over fighting. Not only was he unable to protect her, it was highly likely that he would be a burden to her as well. He could not let the chance that he had sacrificed so much for her to escape, to go to waste. So the mermaid decided to let the female leave herself, whereas he returned to the sea to hold back the snake beast and fight for a chance to save her partners. Even if only one of her partners could survive and leave, it was still a very precious blessing to her."
Gu Mengmeng took notice of this key point - Wang Xiaoxin had agreed to become partners with the mermaid but before they could actualise it, they were separated.
In other words, the mermaid could not make a breakthrough in the restrictions of his level and the highest level he could reach was the third-level.