Your game is better than i expected. With some polish and more levels/content it could be a good mobile game i think. It's not a small achievment to make those assets and the game in a week, especially if you made the game solo. Two feedback about the game i can give you are;
1. Make the player move faster.
2.Add a different swimming animation to the character and rotate the character when it swims up and down.
Nice work! Keep it up!!