Element 115, or as it is known until it is properly named, Ununpentium, is manufactured, it does not occur naturally. No element beyond Plutonium the 94th element has been found naturally. Every element beyond this point has been made by slamming together two smaller nuclei and crossing fingers. The nuclei of these elements are so unstable that they break apart easily and give off other energy such as X-rays and other radiation. These elements have a very short lifetime (on the order of nanoseconds) and decay very quickly.
So why are we manufacturing these elements?
Firstly because we can.
I could end this argument here. Surely that is enough reason. But wait there's more.
The relationship between the structure of these nuclei and their lifetimes has been explored for several decades now and scientists has extracted patterns. They have postulated that although instability has increased in the elements 94-110, there will be a shift towards stability in elements from 110-120 or so. They named this region "The Island of Stability", and have created the treasure map below.
Theories suggested that elements like 115 and beyond would have an unprecedented amount of stability, with lifetimes lasting seconds, and even postulation that we may see superheavy elements in this region that do not decay at all (or so slow we would not notice). So we would have a new super heavy element that in large samples may have properties we would not be able to imagine (no, not Flubber).
Alas the work on element 115 by the Swedes has measured one lifetime at 200 milliseconds. While very stable compared to other superheavy elements, I will not be constructing my giant dinosaur robot out of it.