I'm seeing more and more communities, councils, charities, and groups organising 'Beach Cleans'. Here's a big old list that the Marine Conservation Society has pulled together: http://www.mcsuk.org/beachwatch/events
Good on all of those people who spend their free time clearing up waste that surfs in on the waves from our seas, in order to protect the environment, sea creatures, sea flauna & flora, and ultimately the entire ecosystem. Every day I'm heartened by people's commitment to the cause.
I live next to a beach, so I visit with my dog Geoffrey nearly every day. And every day that passes I see something that has been washed ashore and needs to be picked up and disposed of with immediate effect, in case an animal or person is injured on the beach, or in case it gets washed back into the sea to do whatever unseen damage it may.
Particularly I'd like to appeal to those people, like me, who frequent their beach every day. Don't pass by and assume that someone else will pick this stuff up. Don't pretend you haven't seen it. We're such lucky individuals to be able to spend so much time by the sea and on our beaches, so why not play your part in the deal: the sea is here for us all and it's critical for the survival of humanity (and I'm not even being hyperbolic!), so be fair on our seas, play your part, and pick up and safely dispose of anything that you find that shouldn't be naturally found on the beach or shoreline.
Every time I go to the beach I take a bag in case I need to pick something up (or in case I find some 'ghost gear' - washed up fishing equipment / nets - that can be taken home and actually recycled & repurposed in my artwork). Don't look the other way.
Every day should be a beach clean day. Human beings have put the crap in the seas, we need to take responsibility for taking it out.