Sounds like it's legit - at least the photos don't seem to be fake - but it's apparently a "temporary formation resulting from a "mud volcano," a jet of mud, sand and water that gushed to the surface as the temblor churned and pressurized that slurry under the ocean floor."
http://www.nbcnews.com/science/pakistan-earthquake-creates-new-island-mud-volcano-blame-4B11248003Apparently structures like this have appeared before and have disappeared relatively quickly. The story at the link says that a similar island appeared in 1968 after an earthquake, but it disappeared after a year.