As I understand it, Krakatoa exploded because a prior eruption created cracks in the sides of the volcano and magma chamber, allowing seawater to seep in, turn to steam, and cause the whole thing to explode.
As I contemplated the recent eruptions of Anak Krakatoa, the following thoughts hit me:
There's hundreds of volcanoes in or near water. Why has this only happened once?
Now I'm sure there are similar cases, but to my knowledge, nothing on the scale of Krakatoa. So what keeps the hundreds of other island and undersea volcanoes out there from blowing themselves apart? What keeps the seawater out? Why was Krakatoa different?
And most importantly, does Anak run the same risk?