Board Thread:Theories and Speculation/@comment-35850816-20180611181629/@comment-30207214-20180613001447

What makes Tobirama the best water style user was the fact that he didn't need a water source for his jutsus, while Kisame needed to create a water source on his own with another jutsu to be able to use them (other water style jutsus like shark bomb) on dry land. This was seen against Guy and Bee.