My kids wanted a toy for in the pool, so i thought about making a model of a cocktailracer.I printed mine as is but i think you can scale it to your needs.
Place the boat on the back and print it in spiral vase mode. 3 or 4 bottom layers
Clean sharp edges, make it watertight, color it, maybe its possible to attach RC motor
Drew the boat out of my mind with Onshape after watching a video with cocktailracers.