An undersea earthquake near Indonesia on December 26, 2004 triggered a devastating tsunami that caused over 131,000 deaths in Indonesia due to its proximity to the epicenter. The shape of the beach affected the size of incoming waves, with shallow waters allowing waves to grow larger before reaching shore. While scientists detected unusual wave activity, they did not predict the scale of destruction and most people received no warning due to the unexpected size of the earthquake. Future precautions discussed include tsunami walls, mangrove trees, sirens, and warning signs.