The internet is obsessed with the Fish doorbell livestream - but what is it?

The internet has a new quirky obsession, and no, it's not a viral TikTok dance or a funny pet video – it's a livestream of fish trying to make their way through a river lock in Utrecht, Netherlands.

Known as the "fish doorbell," this fascinating setup lets viewers help migrating fish reach their spawning grounds by simply clicking a button when they spot one on the livestream.

The underwater camera captures real-time footage of the Weerdsluis river lock, and when enough fish are spotted, a water worker opens the lock, letting them pass through.

Now in its fifth year, this odd mix of slow TV and environmental activism has pulled in millions of viewers worldwide.

Sure, most of the time it's just a murky green screen, but as the water warms up, the fish start showing up, turning this slow-moving spectacle into an unlikely source of internet excitement.

"I guess the combination of a good cause, a beautiful story and just a simple idea generates all this attention," ecologist and concept developer Mark van Heukelum said.

Anna Nijs, an ecologist with Utrecht municipality, was surprised by the popularity of the Fish Doorbell, adding: "We get a lot of fan mail from people who think it’s slow TV and they find it relaxing. They appreciate that they can actually do something to help."

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