RedactedNarrative: Operator was paddling down the river without issue until he came upon a tree that was across the river approximately 3" above the water.  He attempted to limbo under the tree lost his balance and his kayak rolled sending him into the water.  He was approximately 30-45 seconds before he was able to pull the manual deployment chord on his PFD.  His PFD deployed and he was able to grab a hold of his kayak.  He was rescued by the Harvard Fire Department. Operator inexperience caused this accident.