They pretty much say why in the project page: renewable energy [tidal, currents?] and cooling. The third, as you mention is latency --they want to be where the people are.
Plus, at depth, storms and typhoons don't affect things all that much, it's rather calm. So, the main threat might be from saboteurs rather than natural disasters [beside the salty environment] because beside a coast guard at the surface [which if contraband coming in is any proxy, it's pretty porous], you don't have a "police presence". So they'd have to rely heavily on monitoring systems.
I think you have the backwards -- sharks aren't attracted to copper cables.. but are attracted to undersea fiber optic cables.. because they carry high voltage power (for the undersea repeaters), which emits an electromagnetic field that attracts the sharks:
I stand corrected, forgot about the power cables I know sharks were attracted to the EM field around the old transatlantic phone and telegraph wires. Well at least it will be a good reason for an outage.
Plus, at depth, storms and typhoons don't affect things all that much, it's rather calm. So, the main threat might be from saboteurs rather than natural disasters [beside the salty environment] because beside a coast guard at the surface [which if contraband coming in is any proxy, it's pretty porous], you don't have a "police presence". So they'd have to rely heavily on monitoring systems.