Do submarines even need cables? That would seriously limit how far they could go wouldn't it? Or does he just mean cables that go under the sea? More explanation needed I think...
The vast majority of the internet links between continents use under sea fibre optic cables, often called submarine cables.
These are the links which allow high speed communication almost all over the globe.
For some areas however cables can't be used (or are too impractical to use) so satellites are used instead.
However plenty of other things rely upon satellites.
Just because internet doesn't come via satellite to everyone doesn't mean nothing does.
The fact that we have a functional GPS system that relies upon satellites and a RE, as well as satellite TV and radio shows quite conclusively that satellites are real.