eddy, whirlpool
漩 centers on swirling water: an eddy or whirlpool, where water moves in a circular, turning motion.
漩 combines 氵 (water) with 旋 (revolve, turn), suggesting water that revolves or swirls. The exact historical development is uncertain, but the phono-semantic structure is plausible.
Water 氵 plus a turning motion 旋 creates a whirlpool: imagine water spinning around and around, forming an eddy.
For セン, picture a whirlpool sending water spinning in a circle: send -> セン, as the eddy sends water swirling.