It's nice to allow players to use powers depending on their position in the race so that they can catch up when they fall behind. The voxel style fits the overall design of the game. I wonder if the waterfall/tunnel will be part of the level design, which would really separate it from a vanilla racing game.

Very nice and concise GDD here. Easy to follow along, clear premise and good plan overall! Personally I would recommend a buffer time towards the end of your production phase to avoid crunch potentially, otherwise great work! Can’t wait to try out drivin that boat. Best of luck!