One great piece of advice I got from Mtn Buzz on this subject is to avoid using Nylon rope or webbing, but to use Polypro based material instead. Nylon is very stretchy when wet.
Originally I used 1/2" nylon, tubular webbing and when it was dry it was tight as a drum, but when it got wet it would get more than a foot of slack in it. I switched to a braided poly 7/16" rope and have had great luck. Hardly any stretch when wet.
Another recommendation is don't tie the rope or webbing directly to the d-rings. feed it through them instead, tying the rope ends off to together, making a continous loop that moves freely through the d-rings. This comes into play if you ever pin or wrap your boat hard on a rock.
To un-wrap / un-pin it, tie a haul rope to the grab line to pull on. Since the grab line isn't tied directly to any single d-ring, it distributes force evenly to all the d-rings. This greatly reduces the risk of tearing a d-ring off your boat, especially if you're using a mechanical advantage system like a z-drag to pull with.
As for knots, I used a small bowline in one of the rope, then fed the other end through it, and tied a truckers hitch to snug it up.
Originally Posted by ShufflingCrew
What is best way to wrap rope around exterior of raft for lifting/transporting raft, having swimmers be able to grab onto something etc? Please be specific (type of knot, how to get rope nice and tight, etc.)