rapid, sand-bank, foreshore
潬 centers on a shallow water feature: a sandbank or foreshore where water flows rapidly. The meanings connect a place where land and moving water meet.
潬 combines 氵 (water) with 單, which likely contributes the sound. The exact historical development of the compound is uncertain, but it relates to water and a sandbank or rapid.
Water 氵 beside 單, which looks like a net or a series of compartments, suggests a place where water is divided by sandbanks or flows quickly over a shallow foreshore.
For タン, imagine a tan-colored sandbank where water rushes: tan -> タン, and the sandbank is the rapid, shallow area.