ELI5 Undersea Cables - who lays and manages the cables that power the internet?

How can just a few hundred cables under the ocean provide the internet to the entire world? Who actually owns and manages these cables? Who lays these undersea cables in the first place? What do these cables look like? Was it a shark or boat anchor that nearly took down the internet in several countries in 2008? 

... we explain like I'm five

Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: tezoatlipoca, newpassionfruit and chaotic_lemming

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