To mark Halloween, 150 teens descended upon a swimming pool in Essex to help mobile network giffgaff recreate the famous Tomatina tomato fight... only this time, with blood and guts. Different takes #giffgaffguts. On October 18, 2013 in Dagenham, England. (Photo by Dave J. Hogan/Stringer for giffgaff)

A swimmer stops short of a red algae bloom at Sydney's Clovelly Beach on November 27, 2012, which closed some beaches for swimming including Bondi Beach for a period of time. While the red algae, known as Noctiluca scintillans or sea sparkle, has no toxic effects, people are still advised to avoid swimming in areas with discoloured water because the algae, which can be high in ammonia, can cause skin irritation. (Photo by William West/AFP Photo)

An animal rights protester demonstrates for the abolition of bull runs and bullfights, three days before the start of the famous running of the bulls San Fermin festival in Pamplona, northern Spain, July 4, 2015. (Photo by Eloy Alonso/Reuters)

The first tram is delivered to the Gogar tram depot on October 17, 2011 in Edinburgh, Scotland. The tram was delivered on a low loader which had driven from Irun, northern Spain and is the first of 27 trams expected to arrive at the depot over the coming months. Last month the Scottish Government intervened to oversee the troubled Edinburgh trams project assigning project managers from Transport Scotland to work with contractors Bilfinger Berger. (Photo by Jeff J Mitchell/Getty Images)

A Syrian youth Khaled from Raqqa walks on snow wearing slippers in the Bekaa Valley refugee camp in Lebanon after the first heavy snow storm hit Lebanon, January 3, 2016. (Photo by Jamal Saidi/Reuters)

Newborn giant panda triplets, which were born to giant panda Juxiao (not pictured), are seen inside an incubator at the Chimelong Safari Park in Guangzhou, Guangdong province August 9, 2014. According to local media, this is the fourth set of giant panda triplets born with the help of artificial insemination procedures in China, and the birth is seen as a miracle due to the low reproduction rate of giant pandas. (Photo by Reuters/China Daily)

Laura Paipo (L), first blind principal in Uruguay participates in a street race with her sighted guide and friend Amparo Bauter in Montevideo, October 4, 2015. Paipo, 55, who took office on August 10, 2015 became the first blind principal of a special school which specializes in the education of visually impaired students. (Photo by Andres Stapff/Reuters)

A concept illustration of the world's first forest in the sky, the Bosco Verticale green twin towers currently under construction in Milan, Italy. Towering over the city skyline the world's first forest in the sky will be a sight to behold. With tree equal to one hectare of forest spanning 27 floors these 365 and 260 foot emerald twin towers will be home to an astonishing 730 trees, 5,000 shrubs and 11,000 ground cover plants. (Photo by Boeri Studio)