Waves that injured surf audience were sneaky, but not 'rogue' - CNN.com

Spectators at the Mavericks Surfing Contest were standing on the beach at Princeton-by-the Sea, California, on Saturday morning when large waves knocked them down. More than 12 people were injured, according to local reports; video of one of the waves was recorded by CNN affiliate KRON of San Francisco.

They were "sneaker waves," waves near the shore that are unexpectedly and significantly larger than others occurring at the time

Sneaker waves are not fun - trust me.