Tsunamis are giant, powerful waves most often caused by earthquakes beneath the ocean floor. Their incredible power can destroy entire communities, then drag the debris out to sea. This video shows what causes tsunamis and the importance of evacuating any area under a tsunami alert. | National Geographic TV

After a massive earthquake triggered the deadliest tsunami in recorded history, multiple waves hit Thailand. As the waves reach the beaches of popular resorts, locals and tourists work together to save lives. Survivors separated by the waves desperately search for their loved ones. Discover the power of the human spirit through stories of hope, hardship, and heroism from the 2004 Indian Ocean tsunami. Tsunami: Race Against Time premieres Monday November 25th at 9pm on National Geographic UK. | N