To earn the Water Suit, you had to win many rounds of Card-Jitsu Water by being the last one standing or hitting the gong before your opponents. After winning a couple of times, Sensei would reward you with parts of the Water Suit; first the Wave Sandals, then the Waterfall Coat, next the Torrent Mask, and finally the Helmet of Oceans. Then you could challenge Sensei in a battle, and become a Water Ninja if you beat him, and earn the Water Gem on your Amulet.