BLOODTHIRSTY SHARKS!
I don't know how the hell they got there, but the water holes on this golf course are infested with bloodthirsty sharks. I don't care how much ninja training you have, there's just no way for you to prepare to fight a friggin shark underwater. Actually, you can somehow hurl your throwing stars at the sharks while you're down there. How the laws of physics can allow this to happen is beyond me, but I guess that's all a part of your master ninja training. Anyway, yeah if you have throwing stars, be prepared to use them on the underwater boards, otherwise, it's nearly impossible to get by without a shark hitting you at least a couple o' times.
So you've survived all of the creatures that mother nature put in your way, that bitch, and now it's time to make your way to the hole. But before you can, you must defeat the flying dragon guardian at the end of each hole.