I see some people are unsatisfied by the some what vague parameters of Jimbei fighting equally against Ace for 5 days, and I admit that personally I don't put much stock into that example since Ace showed very little to put him on an equal level with Jimbei. But how about something more impressive than the thing Shanks did that people still won't stop talking about how impressive it was:
http://www.mangapanda.com/one-piece/574/5
Jimbei blocked a punch that put a hole in Ace, gave Luffy his biggest wound to date, and took off half of Whitebeard's face, with just his bare/fish hands! Something even a Yonko needed a sword to do.
Not only does this show incredible durability and endurance, but it also shows incredible speed as well look how close Akainu was to Ace after his first punch/before his second
http://www.mangapanda.com/one-piece/574/2 http://www.mangapanda.com/one-piece/574/4 Akainu was pretty much on top of Ace but Jimbei was fast enough to move in between Ace and Akainu in the time it took Akainu's hand to move 2-3 feet.
In fact, I think it's also worth mentioning that even though this attack (
http://www.mangapanda.com/one-piece/578/9) went through Jimbei's body, he was still in far better condition than Luffy, who was seriously injured even though he only received the aftermath of the actual attack.
And let's not forget the fact that all of this was after being locked up in Impel Down, which is what Ace fans always bring up in order to excuse his pretty underwhelming performance in the Marineford battle shortly before being killed.
Not only did Jimbei fight his way out of Impel Down ( instead of taking a leisurely elevator ride) , steal a ship from Marines and help fight several other ships on his way to Marineford (instead of taking a leisurely boat ride) , but he also took part in the actual battle at Marineford for a long while ( instead of having a leisurely sit on a platform) , so logically speaking Jimbei should have been way more worn out in comparison to Ace. Who knows how much stronger and more impressive Jimbei could have been if he was 'rested' at the start of the battle
I just can't see Cavendish being able to do a large enough amount of damage to Jimbei to actually take him out. If Jimbei can block magma with his hands he should have no problem with a sword being swung by a small fry like Cavendish.