This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 澚 is uncertain. It combines the water radical 氵 with 粵, but the origin and original meaning are unclear.
Since the meaning is unclear, focus on the shape: water 氵 beside a complex right side 粵. Remember it as a rare water-related kanji.
For オウ, imagine an old man saying 'Oh!' as he stares at this unfamiliar kanji by the water: Oh -> オウ.