Kisame, yes you got that right.
It seems like a lot of people do not analyse the sitatuion carefully at all. Due to kisame's fighting style he produces a mass of water from the start. Therefore the fight would take place in water. The 3rd raikage would know better than to use his raiton armour, if he does both die of electric shock U_U.
Without his raiton armour kisame has a chance, because the surroundings suits him perfectly.
Whilst he can upgrade and fuse with samahada, the 3rd cannot use his raiton armour to increase his speed and durability