Operator was operating an 18ft Bayliner open motorboat on Lake Washington during the annual Seafair event just north and west of Mercer Island (Luther Burbank Park).  The operator said he had over 100 hours of boat experience including the vessel involved in the incident.  

He was pioloting westboaund on the lake and there was heavy vessel traffic due to Seafair celebrations.  There was a lot of 'prop chop' and the wakes were heavy.  While the vessel was near several larger vessels, the boat entered a trough and the bow submerged into the following wave and took on water in the open bow.  The water flowed to the rear of the boat and the passengers in the bow area moved to the rear of the vessel.  The bow continued to sink and took on more water.  The occupants put on life jackets and jumped into the water.  The vessel swamped and then capsized.  

There were no injuries.  The boat was recovered but was a total loss.
Mercer Island                 