Saw this freak 2-3 foot wave moving across Mobile Bay last week. There was not a single ship visible on the horizon.
Freak waves like this is one reason why when on open waters that (sit-in) kayakers wear their spray skirt, even if the waters are calm. By the time a kayaker hears a wave like this coming there likely will not be time to put the spray skirt on.
A 3 foot breaking wave could dump alot of water into kayak or even capsize the kayak if the individual does not have time to prepare for the wall of water.