GEARBOX HELP/INFO NEEDED PLEASE

I was driving my 2003 330I auto individual in the rain , hit a huge dam, about 150mm deep and 5 m wide at about 30km/h, and wanted to pull of at the next robot,..............no power. Seemed like it did not select first. A light on the dash between the S and the D with an exclamation mark came on. Owners manual says gearbox fault, take to BMW. I stay in Middelburg, no dealer and the Witbank one............ok no comment.
Could some contact on the gearbox got so wet and shorted out or is it more serious. Please help any info needed.