overflowing
澰 centers on water rising beyond its normal bounds: overflowing, flooding, or spilling over. The given meaning "overflowing" captures this single clear idea.
澰 combines 氵 (water) with 僉, which likely contributes the sound. The exact historical development of 僉 in this character is uncertain, but the water radical clearly points to a meaning related to water.
The left side is water 氵, and the right side 僉 looks like a container with a lid and people inside. Picture water filling the container so much that it overflows, spilling out everywhere.
For レン, imagine a lens (レンズ) floating on the overflowing water: the lens -> レン, and the water rises around it.