When Itachi visited konoha after the death of hiruzen there was a fight between Itachi and Kakashi. Itachi used water element against Kakashi. In the fight between Kabuto and Itachi in inanami itachi shown his skill in water element.
So it sure that Itachi has water element. You may think that the reason is that Sasuke has lightning element. But in the fight against Raikage Darui used water element against Sasuke( They even had an intel that Sasuke has lighning). In my opinion water element is not a bad option against Sasuke.
So it sure that Itachi has water element. You may think that the reason is that Sasuke has lightning element. But in the fight against Raikage Darui used water element against Sasuke( They even had an intel that Sasuke has lighning). In my opinion water element is not a bad option against Sasuke.