Biology Help? (Pretty basic if you know taxonomy >.<)?

Question

When are sponges and cnidarians motile?

Answer 1

Sponges are sessile in their adult stages. They are usually mobile during their larval stage.

Cnidarians are motile in their medusa stage. Hydra in their polyp stage can also move.

Answer 2

Sponges are not motile but cnidarians e.g. jellyfish, sea anemones , Corals, Portuguese man of war, can be . Hydras are sessile and can twist their hollow bodies to capture food

Sponges are motile however when they release sperm which is carried to sponge eggs where fertilization occurs after which the sponge attaches itself to a rock or another stable surface.