The animals of which phylum are exclusively free-living and marine?

Echinodermata includes free-living and marine animals. It is also known as group of marine animals. Free-living means the ability to move and live independently. Marine – Living in sea. In Greek, ‘echino’ means hedgehog and ‘derma’ means skin. Therefore, they are spiny-skinned organisms. They are found at the bottom of the ocean and in the deep sea. They often make up the bulk of living material. Examples are starfish and sea urchins. Protochordata includes marine animals that are not free-living, e.g. Balanoglossus, Amphioxus, etc. Mollusca - It is the second largest animal group (first largest group is Arthropoda). Molluscs are terrestrial (living on land) or aquatic (marine or freshwater) having an organ-system level of organisation. Examples are snails and mussels.

Platyhelminthes - The body of the animals in this group is dorsoventrally flattened (top to bottom), which is why these animals are called flatworms. They are either free-living or parasitic. Examples of free-living animals are planarians and parasitic animals like liver flukes.