What Was the Hammer of the Waters? Westeros Disaster Hunters - Ice and Fire Theory

What was the Hammer of the Waters anyway? It was something the children of the forest supposedly "called down" to smash the land bridge known as the Arm of Dorne, yes, but what was it? And did the children really do it? How much of Westeros did it affect - what about the Neck and Moat Cailin, for example? This comprehensive examination will explore all the possibilities and present a satisfying answer.