To sum things up and put them simply, Noah decided to play hide-and-seek in a deliberate attempt to make their enemies reveal Eli and Leah's current location.
"Just like what Mother used to tell me about people tending to lose themselves when they're having a fit of pique, it's not that hard to make them spill the beans as well. Seeing that sea serpent hubby and his peculiar children were at a panic-stricken state due to the disappearance of their so-called family, they'd most likely try to step up the game and seize hold on Mom and the Miss before we could. That said, if we made them believe that we already found their location and were now planning to go there, they'd try to get ahead of us," was basically what Noah's scheme all about.