deep, dredge
濬 centers on making something deep or reaching depth, either by nature or by human effort. The dredging sense is a practical application: digging out a waterway to make it deeper.
濬 combines 氵 (water) with 睿, which likely contributes the sound and the idea of depth or insight. The exact historical development is uncertain.
Water 氵 plus the deep, insightful shape 睿 suggests water that is deep or being made deep. Picture a wise person dredging a river to reach profound depths.
For シュン, imagine a shun (avoid) of shallow water: people shun the shallows and dredge to make the water deep. Shun -> シュン.