brimming, rippling
瀲 centers on water in motion at its edge: the brimming fullness of a body of water and the gentle rippling movement across its surface.
瀲 combines 氵 (water) with 斂, which likely contributes the sound レン and carries a sense of gathering or drawing in, together suggesting water that gathers and ripples.
Water 氵 gathers and is drawn together 斂, creating a full, brimming surface that ripples gently.
For レン, imagine a lens (レンズ) floating on the brimming water, its curved surface catching the rippling light: lens -> レン.