Very tiny animals like amoeba do not have any bones. Bigger animals with more than one cell, but not too many cells, can also survive without any skeleton. E.g. Hydra, Jellyfish do not have bones. Some animals like Squid and shark have no bones. They can be as long as 35 feet in body length.
Squids have an endoskeleton, an internal supporting, strong structure of Calcium salts.
It is hard and rigid. Sharks have an endoskeleton of cartilage alone and have no bones though they are vertebrates. We, adult humans, have 206 bones in our body. Nearly all parts of our body have them. The skull and face have 28, the adult backbone has 26 of them.