Alex and Zhou Linfan had to stay on the island until late in the afternoon before they found the opportunity to leave.
The island they went to was far enough from the people according to the formations that the old man had set up around the ocean that let them have a general idea of where everyone was in the ocean.
The old man had apparently also learned about formations while training to be a cook. Becoming a cook was what he wanted to do the most, but he also needed something else to become good at, and he had apparently learned formations too.
While he had never taken tests to show his formation skills, the old man believed that if he did take the tests, he would easily become a Level 8 formation expert.