Sustainable Swim

I was interested to learn actually how plastics such as bottles and carrier bags can be turned into fabrics, and found a gardening website that describes how the process is done to create their gardening gloves.

Step 1. 
Empty plastic beverage bottles are collected, sorted, crushed & baled at a recycling center. Then ground into flakes, & screened and washed to remove caps, labels & contaminants.

Step 2.
The flakes are heated, further screened and cleaned, dried and placed in a vented extruder. The extruded plastic is cooled and then thoroughly chopped to make plastic pellets.

Step 3.
The pellets are sent to a yarn manufacturing facility where they are melted & spun into polyester fiber. The recycled PET fibers are blended with new PET fibers and spun into polyester yarn.

Step 4.
The polyester yarn is sent to a mill for knitting or weaving into fabric. 
Source : http://www.westcountygardener.com/recycled.php

For the use of swimwear, the fibres from the plastics will have to be blended with other materials to give them stretch. An example of a fibre it could be blended with is nylon, which is readily used for swimwear, and can also be recycled.