He has lots of chakra (which is why he can use Taijutsu to that level), but he can't redirect it to cast Ninjutsu at all. To walk on water, all they need to do is to focus their chakra out into a specific part of their feet, which is similar to Taijutsu (redirecting chakra into certain muscles to increase output). He just sucks at changing the chakra to create element-based jutsu.