The pool, as far as I can tell, is built pretty sturdy. Breaking this amount of concrete takes a lot of high explosives, and breaking it underwater is an order of magnitude harder. The Allies at WWII had to go to a great length to damage German dams, while using multiple heavy bombers.

If terrorists were in possession of such amounts of powerful explosives, and a capacity to place them inside a highly guarded area, they could use that to blow up a city center to a much greater destructive effect.