Cat And Girl can be really hard to understand. Go read a few dozen of them and you'll start to get the vibe. It's often told through the two of them having to disjointed conversations over eachother, much of which is just random observations or jokes, but there's usually an element that ties them both together. Also frequent collided sentences like this mix of garbage pail, North Atlantic garage patch, and sour/cabbage patch kids.
So... I think this is a statement of home is never the same as you remember it and that ocean charts that used to use small sea creatures are nothing compared to the new landmarks of the giant garbage patch.
Cat and Girl are sailing back to where Cat was born. It's now covered in water. Not only that, it's now home to the North Atlantic Garbage Pail Kids Patch (which is a reference to the very real North Atlantic garbage patch).
