Short and sweet
The art-style is very original and has its beauty.
As of the things to improve: Add some sound effects or music to improve game's presentation. Add some indicators for where to go (especially the indicator that you have to go down in water, because not all people find it obvious). I would also be nice if you added some content depth, it doesn't have to be much, maybe some collectibles to reduce your final time or boost your speed. It would also be nice if you made the timer visible during gameplay (to make it more speedrunner friendly) and explained the game story (the fact you are diving to the center of the earth) in game.
The game itself is a creative, short experience, good for it's artstyle and going for the best time. While I wrote about many things that can be improved, remember that all of it is constructive criticism to make the game better.
I would also be happy if you played my game.