conceal, hide, lower (voice), hush
潛 centers on moving out of sight or keeping something hidden: concealing, hiding, lowering a voice to a hush, or submerging below a surface.
潛 combines 氵 (water) with 朁, which likely contributes the sound and the idea of going under or being hidden. The character originally referred to submerging in water, and the abstract meanings of concealing or hushing developed from that image.
Water 氵 beside 朁 suggests something sinking beneath the surface. Picture a person holding their breath and disappearing underwater, hiding completely and hushing all sound.
For セン, imagine a secret agent named Sen who conceals himself underwater: Sen -> セン, and he hides silently beneath the surface.