This therapy has been used for thousand of years by the elite and uppermost society class. It make it possible for the Sky People to "fly" underwater by tricking their tail that it is in the air. With only a single session, they can swim and dive underwater like a master even beats them and no need to do it again for the rest of their life. Now it became more accessible to the public and even subsidized by the government. All of the Sky People are encouraged to take this therapy. They may add some spices and herbs to give it more therapeutic effect but that is optional and only available at private clinic. However, the downsides with this therapy is, its quite risky. Leaving someone in that tank with weight on their feet and let them hold their breath near the end and repeating it multiple time caused some of the patients to develop hydrophobia and even death without constant supervising and its even used to purposely drown people in rare occasion. With new upcoming law requiring a medical officer to supervise this therapy, this issues would resolves quite quickly.

Lishi also took this therapy as part of the military training. He is already afraid of water prior to this, giving him some drug solve this instantly. Since he is not a pure Sky People and still taking his lung capacity treatment. He needs more supervision than others. Dr Jiayi is the person in charged on this session. She is a doctor who aboard the airship that arrived at the Tanjong Besi Port. So, they both know each others. The therapy went for 30 minutes before Lishi can resurface by himself with the weight still attached. This can be consider a success. He can now dive with his mermaid friend without worry too much.