Arcana Coelestia # 6346
6346. 'Light as water' means that faith alone does not possess such qualities, neither glory nor powerfulness. This is clear from the meaning of 'being light as water' as having no weight or worth. The fact that faith alone is meant, that is, faith separated from charity, is evident from the things mentioned in what follows that involve Reuben, and that involve Simeon and Levi. Those men - Reuben, Simeon, and Levi - are used here also to refer to faith alone or faith separated from charity.
Josua 19:12
12
und sie kehrte um von Sarid, ostwärts, gegen Sonnenaufgang, nach der Grenze von Kisloth-Tabor, und lief nach Daberath hin und stieg hinauf nach Japhija;