Really solid prototype and I love that you went in a more metaphorical direction of "plant a seed" by showing how individual actions can inspire community involvement (planting a seed of change), which can inspire greater change. I am interested in seeing how you tackle improving the environment beyond the ocean in the next iterations. I love the hand-drawn style and the music too.
Out of curiosity, I did try to see what would happen if the player didn't pick up any plastic and just let pollution meter fill until a potential fail state.