Men slide in the mud during the Boryeong Mud Festival at Daecheon Beach in Boryeong, South Korea, Saturday, July 22, 2017. The 20th annual mud festival features mud wrestling and mud sliding. (Photo by Ahn Young-joon/AP Photo)

A model presents a creation by Colombian brand Elena Plus Clothing at Colombiamoda during Medellin's fashion week in Itagui municipality near Medellin, Antioquia department, Colombia, on July 24, 2017. Colombiamoda will take place between the 24th and 27th of July. (Photo by Joaquin Sarmiento/AFP Photo)

A couple embrace during the start of the San Fermin festival in Pamplona, Spain July 6, 2016. Revelers from around the world kick off the festival with a messy party in the Pamplona town square, one day before the first of eight days of the running of the bulls. (Photo by Vincent West/Reuters)

Festival goers kiss in the “Silent Disco” at the “Music in the Park” stage during the 50th Montreux Jazz Festival, in Montreux, Switzerland, July 9, 2016. (Photo by Anthony Anex/EPA)

Lilly Caron, 8, of Bridgeton, Maine, Jason Homchick, of San Diego, and Lilly's father Jason Caron, (obscured), ride the Sky Swing at Seacoast Adventure, Thursday, July 14, 2016, in Wyndham, Maine. The 100-foot-tall swing gives riders the combined thrills of sky diving and hang gliding. (Photo by Robert F. Bukaty/AP Photo)

Dancers wearing new bikinis perform in front of passers-by and a line of photographers during a promotional flash mob event on a square outside Shinjuku station in Tokyo on July 18, 2016. The event was organized by the Japan Swimsuit Association to promote new swimwear. (Photo by Toru Yamanaka/AFP Photo)

A man strikes a pose in front of a giant torta, or sandwich, during a press conference to promote the 13th annual Torta Festival, in Mexico City, Wednesday, July 20, 2016. The five day festival presents a variety of the Mexican street food made from the most exotic ingredients that include ostrich or stingray, to the classic ham, grilled steak or slow cooked pork. The festival's purpose is to maintain the tradition of eating tortas, and promote the vendors of the Mexican sandwich. (Photo by Marco Ugarte/AP Photo)

The NASA Extreme Environment Mission Operations (NEEMO) 21 mission began on July 21 as an international crew of aquanauts splashed down to the undersea Aquarius Reef Base, located 62 feet below the surface of the Atlantic Ocean in the Florida Keys National Marine Sanctuary. The NEEMO 21 crew will perform research both inside and outside the habitat during a 16-day simulated space mission. During simulated spacewalks carried out underwater, they will evaluate tools and mission operation techniques that could be used in future space missions, including journeys to Mars. (Photo by Karl Shreeves/NASA)