We manufacture throw bags for both swift water and ocean rescue in our Tacoma, WA facility. They all provide an accurate way to throw a line to a victim in the water (or to another boat) and are easy to repack and reuse.
Our 15 and 30 meter models meet Canadian Coast Guard carriage requirements and that is the reason their lengths are expressed in meters. They are constructed using 5/16" floating polypropylene water line which does not kink and is soft to the touch. The 75 foot model has ⅜" water line and is designed for swift water rescue, not that it would not work fine in a salt water environment. Finally we have a 50 foot economy model that has ⅜" MFP polypropylene. This line is not quite as supple as water line, nor will it stand up to ultra violet as well as water line but it does function well and is a fraction the cost.
Throw bags are also useful for ice rescue. We suggest the swift water model since you will need to pull the victim to shore and the added diameter of the line makes that much easier.