This list of rogue waves compiles incidents of known and likely rogue waves – also known as freak waves, monster waves, killer waves, and extreme waves. These are dangerous and rare ocean surface waves that unexpectedly reach at least twice the height of the tallest waves around them, and are often described by witnesses as "walls of water".[1] They occur in deep water, usually far out at sea, and are a threat even to capital ships, ocean liners and land structures such as lighthouses.