Consider a large landmass such as Australia. Imagine if they hypothetically wanted to expand their borders, but they already used up all of their landmass, including the deserts.
Could humanity find a way to push back the ocean? For example, by building a series of gigantic barriers or dams, and then siphoning the water afterwards?
Or is it difficult or impossible to build standing structures in ocean water? Will it be destroyed before construction completes?
Is there any other method for human oceanic expansion? Such as building artificial, floating landmasses? Or by landscaping?
Good answers will explain whether expanding to the ocean is possible, and what methods of expansion do and do not work. Provide references to real-time instances of whether or not it has ever been attempted, if applicable.
Edit: I have done research on this. The difference between land reclamation and what I'm talking about is a matter of scale. I'm talking about expanding to such an extent that you could see a difference on the world map, or from space. I'm talking about creating land from the ocean the size of entire cities, entire countries.
I did not know that the Netherlands was almost entirely reclaimed.
I'm also talking about the potential of doing this in deep oceanic zones, not just shallow waters. The whole point of me posting this question was because I did some research but was unsatisfied by my findings, and because I want to know the scientific possibilities of this type of oceanic expansion.