sound of waves
湃 centers on the sound of waves, specifically the crashing or surging noise of water.
湃 combines 氵 (water) with 拜, which likely contributes the sound. The character is used to represent the sound of waves.
The water radical 氵 beside 拜 suggests water making a loud, crashing sound. Imagine waves slapping against a shore with a 'pai' sound.
For ハイ, picture a high wave crashing down: high -> ハイ, and the sound of the wave is the ハイ reading.
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as the sound of surging water