There are 4 items you have to earn before you can challenge Sensei. 1. Water Sandals. 2. Water Coat. 3. Water Mask. 4. Water Helmet. Tip: To earn points more quickly, talk to Sensei and click "Earn you Water Suit" more, than play on the training mats. You get more points when you talk to Sensei.
I've told you how to become a Water Ninja but what do you do if you don't know what to play? Well, I'm going to tell you! First of all, go and talk to Sensei and click, "Earn your Water Suit".
The game will start in a few seconds once you click the button. Card-Jitsu Water is kind of like the game Frogger. You need to jump from one rock to another but to win, you have to be the last one still standing or the first one to the end. You pick a card and use it to turn off another element. Here's an example:
Once you play for along time and get all the items, it's time to challenge Sensei! To challenge him, talk to him and click the other button, "Challenge Sensei".
It takes a couple tries to beat Sensei, so don't worry if you don't beat him on the first try. When you do beat him, he will award you with the water gem and place it on your amulet.
Congratulations! You are now a Water Ninja! I hope my guide helped you become one.