RedactedNarrative: Operator 1 was operating vessel 1 when the operator let off the throttle causing vessel 1's bow to lower. When the bow lowered it caused vessel 1 to begin to take on water. The operator and passenger 2 moved to the front of the vessel in an attempt to get water out of the vessel. Due to the additional weight this caused vessel 1 to fill with more with water and began to sink. Operator 1 was able to get a pfd on, but the other passengers were unable to locate pfd's due to them being locked in the storage compartment. All of the occupants on vessel 1 sustained injuries (hypothermia) due to the cold water temperatures and passenger 3 sustained serious injuries (diabetic shock). Vessel 1 water damage to the engines from the vessel swamping.