How does plastic bags afect the sea creatures?

What happens to your plastic bags when you have finished with them? Plastic bags take hundreds of years to decompose because they are made from oil. Bags left on beaches end up in the sea and ocean currents carry them to feeding grounds.
Jelly fish are the main source of food for leather back turtles (the biggest turtle under water). Plastic bags look like jelly fish under water so the turtle think it is their food. The turtle's stomach becomes blocked so plastic bags cause a problem for these sea creatures. If Leather back turtles stomach becomes blocked the turtles will starve to death. So by 2030 leather back turtle will be extinct (die out)