sculling oar
楫 centers on a specific type of oar used for sculling, a rowing technique that propels a boat by moving a single oar from side to side at the stern.
楫 combines 木 (wood) with 咠, which likely contributes the sound and relates to the idea of an oar or rowing implement made of wood.
The left side 木 is wood, and the right side 咠 looks like an ear 耳 beside a mouth 口. Imagine a wooden oar shaped like an ear, used near the mouth of the boat to scull through the water.
For シュウ, picture a shoe floating on the water, and you use the sculling oar to push it along: shoe -> シュウ.
voyage