To meet the demand of a rising China, the Australian Navy is taking two very different deep dives into advanced submarine technology.

One is pricey and slow: For a new force of up to 13 nuclear-powered attack submarines, the Australian taxpayer will fork out an average of more than AUD$28 billion ($18 billion) apiece. And the last of the subs won’t arrive until well past the middle of the century.

The other is cheap and fast: launching three unmanned subs, powered by artificial intelligence, called Ghost Sharks. The navy will spend just over AUD$23 million each for them – less than a tenth of 1% of the cost of each nuclear sub Australia will get. And the Ghost Sharks will be delivered by mid-2025.