Exactly!
If I recall correctly, when I was living on Guam for about 4 years, the general local knowledge was that the highest hill on the island itself was in actuality the summit of the world’s tallest mountain that rises up from what is now known as Challenger Deep, back then it was simply referred to as the Marianas Trench.
I’m trying to remember the name of that hill and I think it was called Mount Lamlam (sic) but I can’t be positively sure of that.