Climbing webbing will be just fine if that's what you want to use. Tack on the "marine" label and pay out as arse. I used do a lot of rigging and the climbing webbing is more that sufficient to take the weight.
I've set up numerous slacklines (a tightrope of sorts made from 1" climbing webbing) on a 60' gap with a one inch piece of tubular climbing webbing threaded with another section of 3/8" webbing. The tension on the webbing was so great that in the center of 60' there was less than 2' of sag. I took numerous falls (aprox. 7'-9' drops) Shockloading the line under extreme tension. I'm still here to tell the story and if your in a chest harness taking that much force from waves, etc..you're going to get ripped in half.
Just my .2 cents