We recently got married and we did the Fisherman's Knot ceremony during our wedding. I searched for hours online for the working and couldn't really come up with the exact wording, so our officiant and I kind of pieced together our own (parts from different ones we'd seen) and I thought I'd share. It turned out beautiful so feel free to use....
Knot Ceremony
The fisherman’s knot - “true lovers knot” is the strongest there is; it will not break, and will only become stronger when under pressure (begin tying the knot). These two cords represent your past, your own individual and separate lives before today. As you intertwine your pieces, you are joining your two lives into one, representing the present. The finished knot symbolizes your future, and how your love and marriage will continue to be strong despite any trials life may throw your way.
Although the fisherman's knot is one of the simplest knots to tie, it is also one of the strongest. The rope itself will break before the knot will. (pull the rope together).
I see by this knot before me that you both share the same intentions concerning this relationship, that you will hold each other’s heart tight, and form a strong bond from here to forever.
Let this knot be a symbol of the strength of your love for each other.