It's a fast growing attractive algae of which there are many variations with leaves that look like ferns, grapes, etc. Not surprisingly, the different types are named after the look of their leaves. All grow rapidly by sending out runners which are held in place by root like holdfasts.

Caulerpa is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterranean can have a stolon more than 3 metres (9 feet) long, with up to 200 fronds.