Its finally happened.

If it is water/coolant, the trans is toast.
Water/coolant releases the glue that holds the clutch material to the clutchpak discs and bands.
If it's just foam, then the fluid would look totally normal after an hour or less of sitting.
You can save the radiator by plugging the cooler line connections and using an external cooler.

General rule is water in a trans = rebuild, with converter and lines flush.