oar, paddle
槳 centers on a tool for propelling a boat: an oar or paddle. The meanings are tightly linked to the physical object used in rowing.
槳 combines 木 (wood) with 將, which likely contributes the sound. The character represents a wooden oar or paddle.
The top 將 looks like a general commanding, and the bottom 木 is wood. Picture a general using a wooden oar to paddle a boat into battle.
For ショウ, imagine a show where a performer paddles a boat with a wooden oar: show -> ショウ.