The best starting point by far is at http://www.marinedebris.noaa.gov/ to find out more about the entire ocean filling with our throw aways. NOAA is working to make sure we understand the problem and they continue to add informative maps, best available science, and more. Also, they host conferences you may wish to attend.
I started my journey into making art from plastics much like a street artist in South America........His name is Jhon Jairo Morales Bernal and he was photographed by Jan Socher as Jhon worked his magic, simply burning plastic cups from the trash bins to sculpt little figures. Burning fingers, melting our throw aways, he creates beautiful pieces that call to mind Picasso. Primitive art. Simple figures. Basic materials.
I got away from burning since the fumes and danger of fire are not my style, but do check out Jan's photos of this little known artist at http://www.jansochor.com/ by clicking on plastic art over to the right hand side of his main page.
I hope you can get onto this site to find many many sites with crafty and artsy uses of plastics. Friend, Michelle pointed me to this site and it was here where I got some of the basics that got me fusing:
a whole lotta letters and numbers to get wrong, so please forgive me if I lead you astray........
From my experience, here is a simple way to start fusing plastics you find at the beach, in recyle projects, and other ways............as in our case at Breidablik, collecting bottle caps for over a year............
Step One: Gather some plastic bags and shape into a shape you wish to make (fish, jellyfish, octopus, etc).
Make sure you have about four or five layers of sheet plastics/bags/shrink wrap.
Step Two: Place the shaped plastics between two layers of parchment paper.
Step Three: Iron with a hot, dry iron.
Step Four: Turn over.
Step Five: Repeat ironing, shaping the fused pieces to make the shape a bit more realistic, tucking edges over to allow all the plastics to fuse.
Step Six: Add more plastic to make fins, tentacles, etc, ironing between the layers of parchment paper until you have a finished creature.
Add bottle caps and other soft plastic pieces by applying pressure with iron, always remembering to keep parchment paper between the iron and the plastic piece.
Be in touch with any questions and have fun!