Sui Xiong's super-sized "straw" clone retrieved large amounts of seawater and slowly transported them out of the sea. While he transported the water, his straw body's temperature rose continually, causing the seawater to quickly start boiling. The steam produced did not dissipate but instead rose to the top of the straw where it passed through several spirals that cooled it. After the cooling, condensation occurred, and the freshwater that was created was them further transported. The concentrated brine left in the straw was quickly returned to its normal temperature and released back into the sea.
Such a process sounds complicated, but it could be summarized into the sucking up of water and adding of heat while the brine was cooled and redirected back to sea. The freshwater was then directed to places on the Main Plane which needed it.