Advertisement What's set to become the world's deepest pool is about to start construction in Cornwall – for £150million. The pool, called Blue Abyss and built by a British company of the same name, will measure 164 feet (50 metres) down – about half the size of Elizabeth Tower in Westminster. It will hold more than 42,000 cubic metres of water – equivalent to 17 Olympic size swimming pools or 168 million cups of tea – making it the largest and deepest indoor pool in the world. But it won't be open to the public for a swim – it'll be a research, test and training centre serving the offshore energy, marine, defence and space sectors.