<p>They're not the work of World War II bombs or aliens or fairies. Instead, mysterious underwater rings spotted off the coast of Denmark are the result of poison, biologists say.</p><p>Striking rings of green eelgrass some of them up to 49 feet (15 meters) wide can occasionally be spotted in the clear Baltic water off the coast of Denmark's island of Mon. The formations were captured in tourist photos in 2008 and again in 2011, sparking the type of speculation that's usually reserved for crop circles.</p><p>But biologists Marianne Holmer from University of Southern Denmark and Jens Borum from University of Copenhagen assure that the circles have "nothing to do with either bomb craters or landing marks for aliens." (In Photos: Mysterious Crop Circles)</p><p>"Nor with fairies, who in the old days got the blame for similar phenomena on land, the fairy rings in lawns being a well known example," Holmer and Borum said in a statement today (Jan. 30).</p><p><a href="http://news.discovery.com/earth/plants/aliens-didnt-do-it-underwater-fairy-rings-explained-140131.htm">Keep reading...</a></p>