pure, unmixed, genuine, honest
湻 centers on the quality of being pure and unadulterated: something genuine, honest, and free from mixture or falseness.
湻 is a variant form of 淳. It combines 氵 (water) with 亯, which likely contributes the sound and the idea of something rich or pure. The exact historical development of the 亯 component is uncertain.
Water 氵 beside 亯, a shape that suggests something rich and full. Picture clear water being poured into a vessel, leaving behind only what is pure and genuine.
For シュン, imagine a pure, honest person named Shun who always tells the truth: Shun -> シュン, and his character is as clear as water.