It's become one of the most eagerly anticipated days on the internet.
Every year millions of people from all around the world eagerly tune into a livestream broadcasting from a body of water in the Netherlands hoping to catch a glimpse of a fish waiting at a door, so they can 'ring the bell' to let it through.
Two ecologists Anne Nijs and Mark van Heukelum from Utrecht in the Netherlands introduced the doorbell as a way to allow fish to migrate through the city's waterways as they search for a place upstream to lay their eggs.
They join Emile Donovan.
Fish photo of the day from the Fish Doorbell project Photo: Fish Doorbell Project
