Cessna 172M accident near Ogden, Utah, December 29, 2017

The NTSB's narrative final · quoted from the NTSB record

The commercial pilot and private pilot-rated passenger departed on a local flight in day visual meteorological conditions and climbed to a peak altitude about 2,370 ft above ground level. The airplane then entered a gradual, wings-level descent during which it began to fly over a large lake. The airplane impacted the water and subsequently sank.  The airplane was mostly intact and exhibited no evidence of mechanical failures or anomalies that would have precluded normal operation. Given the condition of the airplane, flight track, altitude data, and the proximity to land, it is likely that the pilot intentionally descended the airplane to low altitude over the lake. It is also likely that the lake exhibited a glassy surface due to low wind conditions about the time of the accident, which would have reduced depth perception and made it difficult for the pilot to judge the airplane's height above the water. Additionally, toxicology of the pilot revealed the presence of three different impairing medications. It is likely that he was experiencing combined adverse effects of these three central nervous system depressants, which contributed to his failure to maintain clearance from the water while performing low-altitude flight.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.

Other NTSB records under N4395R the same tail number, which may have belonged to a different aircraft at the time