Kisame has nothing that can touch Gaara for one. I've also shut down so many arguments in regards to Samehada absorbing Gaara's Sand chakra its not even funny. So if that's an argument you're favoring you should throw it away. What's Kisame going to do? Hold his sword out, and swing it in multiple directions while the sand engulfs him?
Kisame is better off attempting to use Subterranean Voyage. Notice how I said attempt. It takes chakra to manipulate the sand into a swimmable substance. Gaara's chakra vs Kisame own, and while Kisame is focusing on attempting to turning areas of sand in which he'd attempt to swim in, multiple other waves/bullets/etc of sand would attack.
Literally, this match-up is a long dreary one, but Gaara eventually puts down the sand shark with piercing sand techniques, and eventually catching him before he can use his Subterranean Voyage, by grabbing his legs, and what not then crushing them, or by removing Samehada from his grasp etc.
I can go into much further detail, but there is no way Kisame is even pushing Gaara offensively. This become a Med diff just based on the fact that Kisame is so tanky vs Gaara's arsenal.
