Okay so I found the underwater igloo by total accident. I loaded up a random world, walked forward a bit and found a village. One of the villagers were walking away from the village while looking down as if it claimed a job block. So I followed it and it lead me to the igloo. I went inside it and there was a room under it with a brewing stand, hense the villager walking to it.
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Enter -873280664 as the world seed and after the world is loaded up, walk forward until you see a village. There should be a villager walking away from it. Follow him and he'll lead you to the underwater igloo. Or you can just go to these coordinates.