Are sponges mobile organisms

Adult sponges, yes, are stationary. They are anchored firmly to hard surfaces - rocks or coral - and feed through siphoning water through their bodies and collecting food particles. Sponge larvae, however, are free-swimming. After they hatch, they swim and bump along the bottom until sinking and coming to a rest on a stable surface. They then anchor themselves and, over time, become an adult sponge.