If this was your first game, I think you guys did a great job! 3D is always tricky and taking that on for a first project is always a challenge.
For this game, I'd increase the size of the ocean and change the garbage spawning to face one direction so the player can focus on one side of the screen. Besides that, adding SFX and BGM will greatly enhance the user experience.
Keep up the good work! I think you covered a lot of bases for making your first game, and I hope you continue building new experiences. Also kudos for integrating the theme