Per the operators statement he noticed a vibration in the boat at slow speed but the engine was fine at high speed about half way to destination vibration increased so the operator slowed. After entering mckay creek the operator heard a sudden bang, and immediately stopped the vessel. The engine was still running fine but shut it down and within a minute the operator noticed water coming into the boat from the floor level at a rapid rate. All occupants immediately put on life jackets. Another boat came alongside as boat began to sink and they pulled occupants in the other boat. The boat sank with the bow showing above the water. The boat finally sank after they had secured a tow line on the front so they would know where the boat was located. The through hull fitting had failed causing water to enter from the shafts.