Hydras are what you expected - like in greek theories, hydras can regrow their heads whenever 1 is cut off, and multiply them. This is also what this Hydra does. However - it's size is very tiny that it can only be seen through a microscope. Hydras look like a stick with a big circle on their heads, and, of course, tentacles on its circle. Each tentacle slowly regrows each time when one of them is cut off.