overflowing
滔 centers on water rising beyond its bounds: overflowing, spreading widely, or surging in an unrestrained way.
滔 combines 氵 (water) with 舀, which likely contributes the sound and the idea of scooping or drawing out, together suggesting water welling up and overflowing.
Water 氵 beside 舀, a shape associated with scooping or drawing out, like water being scooped so vigorously that it spills over the edges.
For トウ, picture a toe dipping into an overflowing basin: toe -> トウ, and the water spills over.