Ocean Monument not spawing

So I was playing in my survival world, I got the necessary to go to the ocean monument, I look for it by exploring and did found it, then I copy my seed into a ocean monument finder in the web, it told my the coordinates and I went, I turn out it was no ocean monument, and no indication of one been there.

Then I created a world but now in 1.8.9 with the same seed as my survival world, in that world, the monument did spawn.

So it is a snapshot issue