Starfish are marine invertebrates from the Echinoderm phylum.
They are actually amazing creatures, and their physiology is extraordinary.
For example, a starfish can regenerate a limb if one is lost, and often shed them to escape predators (who swim/run away with an arm, rather than the whole starfish).
They also have lots and lots of tube feet, on average around 5,000 of them. The tube feet are the wavy things you can see in the gifs above.
The fastest starfish is the ‘Sand Star’, which maxes out at 2.8m a minute.
A starfish uses water pressure in its body (from having a water vascular system- their blood is basically water) to extend and cause suction on their tube feet, which are also used as gills. They do not have muscles in the traditional sense as we know them, as their body is driven by hydraulic pressure.