Unfortunately, this year I have seen more plastic rubbish on the beaches in South Pembrokeshire than in previous years. 
Worse, I have seen a fair bit in the ocean when swimming, which is really sad as the seas here are normally very clean. 
Yes, it has been stormy lately, but there's been a definite increase in my opinion. 
Why not do your bit when swimming and pick up any plastic you see? 
You can easily stuff it up your wetsuit leg/arm...
Or even tie it around your swim tow strap if it is a big piece like a plastic bag.
Every little helps.
