RICHARD BOUHET/AFP/Getty Images
People look at huge waves along the beach of Saint-Gilles on January 31, 2013 on the French Indian Ocean island of La Reunion as the cyclone Felleng was announced at 735 Km north of the island and progresses at the speed of 17 Km per hour. Felleng should approach the coast of the island from 300 km on February 1st.
A so-called "sneaker wave" is a disproportionately large wave that can sometimes appear behind a smaller one, without warning. Because they are much larger than preceding waves, sneaker waves can catch unwary swimmers, washing them out to sea.
So far this year, sneaker waves have claimed the lives of five people in northern California.