Im "all chain man" but if I was forced to use rope enxtension, I will make colored markings every 5 meters (for the 1:5 scoop) with waveing 3 or 4 pases of thin dark, bright colour acrose rope and leave ends to fluf (kind of paint brush efect with the time), no heat binded ends.
Thread a small black cable tie through the braid at each metre point and pull them tight.
Put in two at the 20m mark and 3 at the 30m mark etc.
I use "self amalgamatin / fusing silicon tape " or permanent marker does the job ok too.
spacing 10 meters
West country whipping with coloured 2mm spectra. Or just use a net hanging knot, clove hitch with a locking hitch, Prussik hitch will work too. Just leave about 3 inches of loose tails and it will be visible for some distance under water.
We use coloured sailcloth, cut in to strips.
10m - blue
20m - yellow
30m - red
40m - green
50m - purple
Poke the cloth thru the rope a few times, each marking has a couple of pieces so if one wears or goes missing there's back up. Re new every season.