Kisame can use high level Water techniques as we all know. What people forget is that Jiraiya can use high level Earth techniques that likely match Kisame's scale.
And it's a fact that
Water has a weakness to Earth - this means the Water jutsu will only make the Earth jutsu stronger.
There is no reason for us to believe that Samehada can control natural energy. Samehada is a
sentient living entity. It can't mold natural energy - it doesn't know how.
When Jiraiya was
drugged by Tsunade's poison and
couldn't mold his chakra properly, he was still able to use Yomi Numa to the point of
sinking Manda:
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Jiraiya even says that it was "such a small swamp". If that was a small one, then how big is a full-sized one?
If this doesn't get the point across that Jiraiya can use techniques of monstrous scale, then I don't know what does.
Combine the above reference with a healthy Jiraiya who can use his techniques to 100% effect and with Sage Mode, Jiraiya wins.
I don't see how Samehada would be able to absorb,
Sage Art: Goemon
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Katon: Gamayu Endan
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If there's anyone in the Naruto world who can match techniques of Kisame's magnitude, it is Jiraiya.
Jiraiya could also capture Kisame and take him on his own turf using his Gama Hyoro:
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I don't care how good Kisame is at using Water techniques.
He can't swim around in lakes of corrosive gastric acid.
If Jiraiya was able to capture Animal Path into this technique while being
outnumbered with all 6 of the Paths on the field
with one of his arms ripped off, I don't see how he'd have a problem getting Kisame in this.
And to people who think Kisame's Water will help against Jiraiya's oil and fire:
HAVE YOU EVER TRIED ADDING WATER TO BOILING OIL?
Enough Said.