Kisame vs Itachi

[Zexion~]

He has sunglasses, not goggles.

With his body? Yeah. With Susanoo? Meh. Then there's always Genjutsu. His main issue underwater is mobility, but he doesn't need to be mobile when he has Susano. Kisame's still at a bigger disadvantage though. Human Path was blocking Jiraiya's attacks without eyesight, something that Jiraiya said isn't possible with only chakra sensing.

Still protects the eye from water flooding in seeing as he's an octopus Jinchuriki I wouldn't be surprised if they were waterproof

Anyways my man Pain doesn't need to be brought into this we all know the reason why they could do what they do. Even Susano'o is effected underwater due to its massive size its speed is going to be reduced even more? As its more pressure acting on the object, the bigger you are the more resistance acts on your movements swinging totska will be extensively slower
Also don't forget Kisame's eyes are more horizontal now (On opposite sides of his head) So it would be harder for Itachi to get that stare going for Tsukuyomi lml