Flatworms, as the name implies, are a flat soft-bodied invertebrates. And they are really flat. An average flatworm is as flat as a bunch of paper sheets stacked together. Flatworms do not have any circulatory and respiratory organs – they consume oxygen by diffusion.

Flatworms often confused with nudibranchs. They are about the same size, shape and color. The key difference between nudibranchs and flatworms are rhinophores, which the latter don’t have. Flatworms are also symmetrical. That means that left and right, front and back, top and bottom sides are identical. Unlike the nudibranchs, flatworms are very delicate and tear easily, so don’t consider picking them up. Also opposite to nudibranchs, flatworms move around much faster.

Flatworms are also less common in Maltese waters. You are likely to spot a nudibranch on your dive rather than a flatworm. Some species like the punctuated or darkspotted flatworm considered alien to Maltese waters and Mediterranean region. They are native to Indo-Pacific region and have only been spotted around Malta in 2015, during a marine survey by the Conservation Biology Research Group.