How did the 2004 Boxing Day tsunami go undetected and why was it so devastating?

First came an earthquake deep below the Indian Ocean. Minutes later, in the early hours of Boxing Day 2004, a 100-foot wall of water ripped through Indonesia.

Then the Boxing Day tsunami reached Thailand, leaving unimaginable devastation in its wake.

Using eye-witness accounts, BBC Select presents this gripping documentary investigating the horrific natural disaster of the 2004 tsunami.

Could the catastrophe have been averted?

Watch History's Deadliest Tsunami and more acclaimed documentaries on BBC Select today. Restrictions apply*.