Cool game. I love that you found a way to frame the theme around a real world issue so props for that.
There were a couple areas to improve I picked up on.
I wasn't entirely sure why I was collecting the goal objects (rattle/microphone?, Phone, and sunglasses). Maybe to woo the whale we see in the end panel? It would've been cool if the goal object maybe helped to resolve the core conflict of your game in some way, being the plastic in the ocean.
Also in terms of gameplay I found the optimal strat was basically just to stay as low as possible and spam space bar, once I found that out the game felt a lot less challenging and so less fun.
Finally, it seemed that you played as three different whales on each level based on the colour change but your health never resets as a new whale which seemed odd.
But yeah great application of the theme and good work! Save the whales!