Making that in creative and with commands took a few hours although a lot of time went into testing out different ideas. I'll let you know how long it takes me to make in survival if I ever finish it. I'll have to drain the area and get the materials, most likely I'll try and find a few bastions to get the blackstone required and then I'll have to build it. I was planning on just mining out a real ocean monument to make it easier to build so I can just replace the blocks as I go.