What is the length of the world's longest swimming pool in metres?

The world's longest swimming pool is indeed 1,500 metres long. This immense structure is located in San Alfonso del Mar, a resort in Algarrobo, Chile. It holds the Guinness World Record for the longest swimming pool in the world. The pool's impressive length allows for a unique swimming experience, as it stretches over a kilometer, making it not just a swimming pool but a significant attraction for visitors. The engineering and design involved in creating such a lengthy pool are remarkable, showcasing innovations in construction and water management.

While other lengths mentioned in the choices are significant, none match the astounding 1,500 metres of the actual longest swimming pool, emphasizing the pool's unique position in the world of aquatic facilities.