RedactedNarrative: V1 was paddling upstream on the des moines river and going under the nw 66th ave bridge immediately downstream of the sycamore boat ramp. Witness stated he watched v1 go under the bridge and lost sight of it behind the bridge pilar. When witness looked again, v1 was overturned and floating downstream with no site of the occupant. Witness was approximately 3 tenths of a mile upstream and immediately paddled down to v1. Witness pulled v1 to shore and realized that the operator of v1 was stuck inside the kayak. Witness knew immediately that the operator was dead.  Both individuals were wearing a life jacket and both individual were avid paddlers. Witness verified that the current was extremely turbulent and strong underneath the nw 66th ave bridge.