island
嶼 centers on an island, especially a small island or islet, often in a poetic or geographical context.
嶼 combines 山 (mountain) with 與, which likely contributes the sound and may relate to the idea of a raised landform. The character is used for small islands or islets.
The left side 山 means mountain, and the right side 與 looks like a complex shape rising from the sea. Picture a small mountain peak poking out of the water as an island.
For ショ, imagine a small island with a single showy palm tree: show -> ショ, and the island is the stage for that show.