Front loader washing machine
The best option is to take it all to the local Laundromat. Put it all in a front loader, and it will get all of the sand, grit, mold, growth, out and the line will be nice and soft. Don't use a top loader, since the line will just clog up the center agitator, or wrapped around it.Every few years, I take my haylards and sheets to get them washed. Every spring, I get my dock line washed.