I am not a really good coder so the controls might be weird. If you want to change the map, you have to hover your mouse over the change map and click on these numbers: 1 is the Mountains ( you will fly up and up and up) 2 is the coral reef ( the current will sweep you) 3 is the haunted forests (ghosts appear at some point) 4 is the Savanna (no effect) BTW, before every time you change the map, you will have to stop the game and click the green flag. (you will have to do that after every round, like stop and click green flag)
I made this all by myself, but got the idea while watching the DragonBall series.