Generally the line will be 1/4", 5/16" or 3/8" polypro. Poly is inexpensive, it floats and is normally in a highly visible color. The 1/4" line may be appropriate for many boats as it is doubled up between the boat and shore. The line gets fed from the boat, around a fixed object on shore and is brought back to the boat so you can easily retrieve the line when you are ready to depart.
Here is a recent discovery that may be great on smaller boats (up to 40-footers?) as it can carry about 400-feet of 1/4" poly line.
Alert Stamping 7000WR Pro-Reel Cord Carrier
My last post with a stern line generated much interest. Since that time I have heard that Mr. Brooks no longer makes his reels. See: http://americantugnews.blogspot.ca/2012/11/stern-tie-reel.html. That reel held more line and was appropriate for larger boats or those wanting to carry larger diameter line.
The new reel has been sent off with a client aboard his American Tug 395 for field trials in Desolation Sound. A report will follow later in the summer.
We still are looking for the best stern line reel solutions. Please submit your solution to: firstname.lastname@example.org.