Looks loke mud pit and puddles took its toll!! Gotta take starter motor off and clean it!!! Any recommendations on what to clean it with? CRC is my best guess!
You can buy electrical contact cleaner from Jaycar (about $9 a can) or MAFS cleaner which is the same stuff from SCA for about $17 a can. It leaves no residue, unlike WD-40 and other spray lubricants/water dispersants.
You could use the other products and finish with the electrical cleaner. I'd pay close attention to the metal parts, particularly the bearings, in case there was any corrosion created by the water that got in.