On February 28, 1997, approximately 1830 central standard time, a Cessna 152, N49205, collided with power lines and descended into the Mississippi river near Plaquemine, Louisiana. The two occupants, a certified flight instructor and a student pilot, received fatal injuries. Instrument meteorological conditions prevailed in the vicinity of the accident site, and a VFR flight plan was filed. The instructional cross-country flight, operating under Title 14 CFR Part 91, departed Lafayette, Louisiana, approximately 1720 and was en route to Reserve, Louisiana. According to seven witness observations of people who were working on a levee adjacent to the accident site (all attached to this report), the aircraft was in level flight, cruising over the Mississippi river at a low altitude beneath low clouds. One witness recalled seeing the aircraft approach high tension power lines which were traversing the river and perpendicular to the flight path. He reported that the aircraft impacted the lines, became hung up momentarily, and then fell into the river. He further reported that the aircraft remained afloat for approximately 10 seconds, and then submerged. Five of the witnesses heard the sound of an engine and did not report that they felt the aircraft was in distress. According to local utilities personnel, the 2 power line support structures, located on each side of the wire span, were 425 feet in height. According to FAA records, Baton Rouge Approach Control was communicating with the pilot approximately 5 minutes prior to the accident and were providing VFR flight following through the Baton Rouge area. They reported that the pilot did not report any abnormalities with the aircraft. According to FAA records, the pilot got weather briefings from Automated Flight Service Stations before and during the flight. Initial rescue and recovery attempts by the coast guard and local emergency personnel were hampered by foggy weather conditions. However, on March 2, 1997, the wreckage was located and recovered. Recovery personnel reported that both occupants were still belted into their seats (lap and shoulder harnesses) and there was no sign of egress. Examination of the wreckage by an FAA inspector revealed wire strike marks beneath the right wing near the wing support strut attachment point. Throttle and mixture levers were both full forward, the carburetor heat was "off", and flaps were not extended. The tachometer needle was found at 2,500 RPM. Both propeller blades were bent rearward and were attached to the mounting flange. Control cable continuity could not be verified due to impact damage. Autopsies and toxicology testing on both occupants did not reveal any abnormalities.