I prefer 5/16" rope to 3/8" rope as it is still thick enough not to cut into your hands and has plenty of strength for painters. I have had very good luck with BlueWater river rescue ropes and have yet to see one fail. The variety I prefer is their R-3 rope. It is of kernmantle construction with a braided sheath over a stranded core and is 100% polypropylene so it floats very high. It ties well and seems to be quite UV resistant. I have not found it at 50 cents a foot but you can get a 300' spool for under 64 cents/foot and free shipping here:
http://www.austinkayak.com/products/7241/BlueWater-Ropes-516-River-Rescue-Rope-BW-R3-300-ft.html
If you sign up for ACK's email list they will send you monthly coupon codes for 15% off one item which would bring the price down to around 54 cents/foot.
http://www.austinkayak.com/products/7241/BlueWater-Ropes-516-River-Rescue-Rope-BW-R3-300-ft.html
If you sign up for ACK's email list they will send you monthly coupon codes for 15% off one item which would bring the price down to around 54 cents/foot.