National Sea Serpent Day is observed worldwide every August 7, commemorating a famous sea serpent sighting by the crew of HMS Daedalus in August 1868. This holiday celebrates the mythological concept of sea serpents, also known as sea dragons, which are prevalent in various mythologies and symbolize the clash between chaos and order. Participants often engage in learning about sea serpents and other sea monsters from different mythologies, sharing their knowledge and enthusiasm through social media using the hashtag #NationalSeaSerpentDay. The origins of the holiday are unclear, but it has been recognized since at least 2009. Notable examples of sea serpent myths include the battles of gods and heroes against these creatures, such as the slaying of Leviathan in the Hebrew Bible and the defeat of Tiamat in Mesopotamian mythology.