There's a couple of things I should point out at the start. First of all, the most astute of you will know that a league is a unit of distance, not depth. So when they say The Phantom From 10,000 Leagues, it should really be The Phantom From 10,000 Fathoms. But if it was from 10,000 fathoms it would be from roughly eleven miles deep in the ocean, or more than the depth of the Marianas Trench, which is substantially more than the twenty feet of water we see it in. Which brings me to my second point. If we can actually see it, then it's not a phantom. It's actually more like The Creature From The Black Lagoon's hillbilly cousin. So in short, it's not a 'Phantom' and it's not from '10,000 Leagues', but in every other way the title is completely accurate. It's definitely 'From'.