A pair of divers explore the wreck of the Giannis D (originally Shoyo Maru) on the Abu Nuhas reef, Strait of Gubal, Red Sea, Egypt. By British photographer Alex Mustard. He's travelled the world snapping pictures of wrecked ships lying on the sea bed.
"Mammatus clouds are most often associated with the anvil cloud and severe thunderstorms. They often extend from the base of a cumulonimbus, but may also be found under altocumulus, altostratus, stratocumulus, and cirrus clouds, as well as volcanic ash clouds. When occurring in cumulonimbus, mammatus are often indicative of a particularly strong storm or perhaps even a tornadic storm."