RedactedNarrative: On 1/3/2017, at approximately 4:44 pm, Agent was advised that a single vessel had struck a submerged unmarked dredge line at the mouth of Deer Island Bayou in St. Mary Parish. After speaking with the operator, it was learned that Operator was traveling south in the Atchafalaya River and struck an unknown object upon entering the mouth of Deer Island Bayou. Operator was traveling with one passenger. Operator advised that the impact caused himself and occupant to fall forward and impact the console and windshield of the vessel. Operator stated he then stopped the vessel to see what he had hit, Operator then stated that he identified the object as a submerged unmarked dredge line. He was not wearing an engine cutoff switch and both subjects were not wearing a PFD at the time of the incident.