ford stream, wade across
涉 centers on moving through water on foot: fording a stream or wading across. The idea extends naturally to any shallow crossing.
涉 combines 氵 (water) with 步 (step, walk), suggesting stepping through water. The modern form is a simplified version of an older character that also involved water and walking.
Water 氵 on the left and walking 步 on the right: picture yourself stepping carefully through a shallow stream, wading across.
For ショウ, imagine a show where performers wade dramatically across a stage stream: show -> ショウ, and the water splashes as they ford it.