some of the water ride ideas i have are boat fights where u need to destory the other person's boat, a boat rollercoaster with water, a boat race where u have to race each other on boats, the giant cannonball where u need to jump in to 1 block of water(you may die so you should sethome), bumper boats, and finally a water maze where u have to find air pockets in order to breathe or else u drown. Some these do involve deaths but to be safe, put up a warning sign saying "u may die here. I warned you." if u can put these ideas in, i would help you build them.