Kisame while fused with Sameheda and inside the Water Dome, takes on features and abilities of Sameheda that allow him to casually avoid and counter Gaara's attacks while shaving through Gaara's defense. To explain Kisame with the Sameheda fused with him gains the abilities to
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,
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by simple contact and
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. While Kisame is in the water Dome and fused with Sameheda he becomes Shark like and becomes faster underwater. So fast that he began catching up to Verison 2 Killer B.
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How will this be affect against Gaara?Gaara while Gaara is capable of manipulating sand that is wet it is mention that the Sand becomes much heavy. With Gaara's Sand being heavier it causes it's attacks to slow down. So using the Sand underwater would be slow. This along with Sand without chakra being slower and Kisame's movements being increased he could avoid all attacks with ease. If Gaara uses the Sand with Charkra he may be able to capture Kisame, but even if this was possible which it barely is, Kisame being able to absorb Charkra on contact would absorb the chakra inside the sand and be capable of using the spikes that he can produce on his body to shred the weake sand off his body. While in pursuit of Gaara, Gaara using his Chakra sand to defend himself, would be useless because Kisame on Contact would absorb the Chakra and Shred through it easily. Gaara's sand would be to slow to attack and being made out of chakra would not be able to defend seeing as Kisame on contact would absorb and shred through it. Gaara's non chakra sand is to slow to defend him in time or attack quick enough underwater while being heavy and kisame having his speed boosted.