Bobbed up means something that has appeared or surfaced unexpectedly. Its antonyms can be words like disappeared, sank, submerged, and vanished. These words imply that something has gone out of sight, disappeared or hidden beneath the surface. Some alternative antonyms for "bobbed up" include words like sank, plunged, plunged, and submerged. These words suggest that something is no longer visible or present on the surface. Conversely, bobbed up antonyms can also be words like emerged, surfaced, or ascended. These words imply that something is appearing or coming into view, rather than disappearing or hiding.