Stunning photos have revealed incredible secrets of the underwater world, with the winners of the 2018 Underwater Photographer of the Year award announced. German photographer Tobias Friedrich has been named Underwater Photographer of the Year 2018. More than 5,000 images were submitted this year by photographers from around the world. UPY was once again kind enough to share some of this year's honourees with us below, with captions written by the photographers.
