Is is possible I have shorted out a switch or sensor on my transmission?

I got in some high water yesterday and now my transmission is doing something weird.

First the selector does not show what gear I'm in either by the shifter or on the dash display.

The "M inside the gear" indicator light is staying on.

It feels like I'm starting out in 2nd or third gear and I cannot hear/feel the transmission change into a higher gear as I drive. My transmission has always shifted smoothly anyway, but the engine RPM's stay high even when I'm going highway speeds.(2500-3000) normally once I'm in top gear, the RPM's settle around 2000-2200.

Thanks in advance for any help you can provide.

 

is you truck only running in 3rd gear?

 

Yeah I believe so.