So. I see a LOT of Squirtle as *insert favorite TMNT here* fanart. Let me give you some insight:

Shredder is 6'2'', 220 pounds of muscled anger, clothed in spiked body armor. He's well trained in bare-handed and weapons based martial arts. He has an entire robotic army of minions that will gladly die for him, and he can just build more. He has numerous equally muscled henchman under his belt, who own guns. He routinely fantasizes about eating turtle soup, and it usually takes all four seasoned ninja turtles to defeat him, sometimes with Splinter's assistance.

Squirtle is barely over a foot tall. He weights less than 20 pounds. He has never had any formal martial arts training, much less any fighting training at all (assuming he's just been caught.) His signature move is shooting bubbles. He can't effectively communicate because he can only say his name. He can hold a weapon in his mouth, but he can't be particularly agile (Unless hes like level 100 squirtle from Super Smash bros. but I digress), but I've yet to hear of ANYONE EV training a Squirtle for speed.

If you pull a Squirtle out against Shredder, he will not faint. He will DIE. And then get eaten by a big buff samurai.

I love you Squirtle, but you're just not ninja material. Level up to a Blastoise, and then we can see about putting you up against the Foot.