I heard a story some years back about the origin of that fabric. (I may be mixing two stories here but they are both good!)
Sailors on "traditional" vessels didn't like the standard Dacron being foisted upon them and were always on the lookout for something more "authentic." One day, a gnarly-fisted skipper was outside a pub and leaned for support on a lorry (that's what they call a truck in England). His hand grasped something that had a nice soft feel to it . . . the tarp covering the load. He took a closer look and it had a nice tight weave but was pliable . . unlike his Dacron sails.
Anyway . . . . some time later, the story got to North Cloth, who then began to experiment with warps and wefts and things to come up with a similar material that would work on sailing ships. When they got it right, they also wanted to get the color right, so they looked at the paintings of James Butterworth.
They got the cloth and the color . . the cloth is Oceanus. Old Ironsides had some sails made of it . . nobody could have worked with the cotton of the originals . . .
I bet not many of you have a seabag made of Oceanus . . .