close up, freeze over, congeal
沍 centers on the idea of something liquid becoming solid and still: freezing over, congealing, or closing up as if sealed by ice.
沍 combines 氵 (water) with 互, which likely contributes the sound and may suggest mutual or reciprocal action, though the exact historical development is uncertain.
Water 氵 beside 互: imagine water molecules mutually locking together as they freeze, closing up the surface.
For ゴ, picture a frozen pond that looks like a solid go board: go -> ゴ, and the water is frozen solid.