sink
湮 centers on sinking or submerging, often in water or obscurity. The meaning is narrow, focusing on the act of going under or being buried.
湮 combines 氵 (water) with 垔, which likely contributes the sound and the idea of blocking or burying, giving the sense of sinking in water.
Water 氵 on the left and 垔 (which looks like something being covered by earth) on the right: imagine water flooding over the earth, causing everything to sink.
For イン, picture an inn sinking into a flooded marsh: inn -> イン, and the water 氵 makes the inn sink.