Police are appealing for information after a fatal collision at Billingborough Fen, between Grantham and Spalding.
Officers were called at 4.27pm on Wednesday after receiving a report of a vehicle submerged in a dyke at Main Road, Billingborough Fen.
Officers attended the scene and found a silver Vauxhall Astra in the dyke. The driver, an 86-year-old local woman, had died.
Police say it is not clear at this stage how long the vehicle had been submerged in the dyke, but officers are appealing for anyone who thinks they may have seen it in the area over the last couple of days to get in touch with them as soon as possible.
Anyone with information should call Pc Robin Dunn at Lincolnshire Police, quoting incident number 288 of May 15.