RedactedNarrative: O1 was fishing on Bear Butte Lake when he went to adjust his seat to a different position on V1. The seat locked in on one side but not the other, causing O1 to become unbalanced and V1 to tip over. O1 attempted to get back onto V1 but it kept tipping over. V1 grabbed his PFD from the seat area and put it on one side of his body but never fully wore it appropriately. O2 who was not involved with V1, observed O1 struggling and went toward O1 to offer assistance on V2(kayak). O2 grabbed O1 and O1 grabbed onto V2. O2 paddled V2 and O1 to the shoreline. O2 called 911 and informed them what was going on. An ambulance and SO were dispatched. O1 was transported to the hospital for Hyperthermia. WCO and the SO recovered V1 from the Lake and loaded it O1's truck and trailer. WCO went to the hospital and interviewed O1. WCO learned that O1 had purchased V1 a few days prior to the incident and had no experience using it prior to the day of the incident