I'm also thinking Jiraya could beat him. Even if Kisame pulled the GWSB jutsu, I think Jiraya still wins (at very high diff) as long as he can go sage mode. Because of his ability to use the toad genjutsu, which I don't believe we have seen Kisame faced with a genjutsu of that level, he could be able to defeat him. Also his underworld swamp technique is one he could use to trap Kisame. Finally Itachi says Jiraya is stronger than him, Kisame is obviously weaker than Itachi.
For those who talk about water dome, i hope you realise Kisame needed Hachibi's powerful chakra to create one that huge and that in this fight, he won't beneficiate of such a huge quantity of chakra. So his water dome should clearly be much more smaller. Also even if we considerate he can create a water dome of that size with his chakra alone, when you compare the size of the water dome with Jiraya summons, you could clearly see that they are roughly from the same size:
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So Jiraya should have no problems fighting there with his summons especially when we know that toads actually like fighting on/under water
For those who think Kisame, who is known as the tailless tailed beast because of his comparable chakra reserves to that of a bijuu, who never tires, and never shown to have even come close to chakra shortage, doesn't possess the amount of chakra to create a Water Dome the size of the one he created while fighting Bee on his own, just understand that without the Hachibis power,
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As well as creating an entire lake that is 10 stories deep with less then
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As if that wasn't enough, without the aid of samahada transmitting chakra to him as he chooses, he was able to create
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, as well as
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Take note of the massive size of this jutsu, that is Kisame in the top right, a mere ant.
And if we were to compare the size of jiraiyas toad summons to a nearby structure rather then mountains miles into the background it's more like this
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Or even more accurately we can compare tree sizes to the two.
Trees compared to Gamabunta are about 1/3 his size.
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While trees directly underneath Water Dome are small bushes.
I don't get why you would restrict Kisame's GSB seems a little un-fair.
In my opinion it depends if Kisame know's about Jiraiya's SM or not, I say this because if Kisame attempts to absorb Jiraiya's SM chakra in theory couldn't that kill Samada..?