KanjiJLPT N1
Rapids

rapids, current, torrent, shallows, shoal

Mnemonic

A storm sweeps through the gorge, hurling a bundle of driftwood into the river. Each plank spins like a page flipping in the wind as it's dragged through the roaring rapids. The bundle breaks apart, logs slamming against rocks, page after page of debris churning through the rapids until nothing remains.
Additional thoughts
Picture the storm feeding the river, the bundle of logs acting as visual proof of the current's power, and each piece flipping like a page to emphasize the chaotic, fast-moving water.
Quick recall
A storm flings a bundle of logs flipping like a page through the rapids.

Details

The keyword for 瀬 is rapids. This kanji refers to shallow, fast-flowing sections of a river where the water rushes over rocks and stones, creating turbulent currents. It evokes the image of a riverbed where the water is not deep but moves swiftly and forcefully. By extension, it can also suggest a critical juncture or turning point, much like navigating through dangerous waters.
On'yomi
らい
Kun'yomi