1.) Yes, sharks have had a history of biting the cables, however it is not one of the biggest threats to the cables, and it certainly is not a frequent event.
2.) Anchors that are dragged across the cables are a common way for them to break along with damage from fishing vessels. Events like earthquakes and tsunamis can harm the cables and intended damage or damage caused by aquatic animals can occur but is not as frequent.
3.) People on the internet all over the world use submarine cables. This includes telecom carriers, mobile operators, multinational corporations, governments, content providers, and research institutions who use the cables to send data.
4.) Cables are about the thickness of a garden hose that has a few layers to increase it protection and durability. Some of these layers include silicon gel, copper sheath, and steel wires.
5.) One end of the cables fires lasers that are carried through the glass fibers to reach the receptors at the other end.
6.) What interested me the most about these cables was the size of them. Before reading this document, I pictured very large and thick wires roughly the width of an oak tree. I figured that since the wires have such an important job that they'd need to be large to gain protection but because of technology, the cables do not need to be this size.