This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
涽 combines the water radical 氵 with 昏, which likely contributes the sound. The exact historical development is uncertain.
Water 氵 beside 昏 (dusk, dark) suggests murky or confused water, but the exact meaning is unclear.
For コン, imagine a con artist stirring dark, murky water: con -> コン, and the water becomes confused.