Sal's Dad wrote:
Consider a knot - or, more precisely, as you are joining two lines
together,
a bend. Several can be found, with animated instructions, at
http://www.grogono.com/knot/ .

You could also fasten the tow line directly to the fitting on the
tube. I
seem to recall there being a rationale for NOT taking this approach,
but it
escapes me at the moment.


Or, you could use a hitch, a rolling hitch works well.