RedactedNarrative: Vessel was travelling north bound in front of the dam on the south side of the concrete structure of the dam.  The vessel had 3 occupants in the bow of the boat.  The vessel came over a large wave and the bow went into the next wave.  The vessel took on a great deal of water and swamped, causing it to sink.  Vessel #2 responded to help the occupants of vessel 1.  While doing so, they swamped and capsized due to the heavy weather conditions.