[matthewh (OP)]

Paul has sent us in this question on plastic pollution:

Is there any chemical which could be added to plastic which would repel sea creatures, or would such a chemical just be leached from plastic by the effect of sun and chemicals in the sea?

Let us know what you think of the idea!

[Bored chemist]

It is very rare for the solution to "too many chemicals" to be " add more chemicals".
Apart from anything else, where would you repel the sea creatures to?
Where could they go?

[evan_au]

Many repellent chemicals are toxic themselves, in sufficient concentration.

Even if they aren't toxic, they would disturb the sense of smell, finding food, predator avoidance and general marine behavior.