waht happend wen the transmission have water

Water in the transmission? Is it green anti-freeze or was the car in a flood? In any case you must get all the water out or the transmission will be ruined. Change the fluid and filter and maybe have a transmission flush. Or you could change the fluid several times after driving it for a few miles between changes. Anti-freeze in the trans means a leaking radiator.

It is most likely due to the cooling tubes in the radiator corroding. The transmission fluid is cooled by a few separate cooling tube/fins combined with the radiator and engine coolant. When the internals fail for these designated cooling tubes, engine coolant can seep in causing the water in the fluid. I would highly suspect the radiator has failed.