It looks too small, perhaps there's more water tied up in the core and mantle than that?

[1] https://www.bnl.gov/newsroom/news.php?a=111648

[2] https://www.space.com/water-in-earth-core-forms-crystal-laye...

[3] https://www.goethe-university-frankfurt.de/125691203/An_ocea...