This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 砅 is uncertain. It visually combines 石 (stone) and 水 (water), but the original meaning and component relationship are unclear.
The kanji shows a stone 石 beside water 水, but its meaning is unclear. Imagine a stone skipping across water, but remember that this is just a visual hint, not a confirmed meaning.
For レイ, picture a ray of light reflecting off a stone in the water: ray -> レイ.