To be honest, I would think sailing should go down in this case. Especially since after scouting so many coast tiles at this point, and we don't even have a single damn piece of crab-meat.
Now, on the other hand, I think I know what you are getting at. You want the trade-routes right?
Of course, if we are all isolated by ocean then it doesn't really do a damn thing for us, except for internals.
But one thing I am damn sure about, the Ragnar team is doing cartwheels on this map after getting such a huge advantage. And without a doubt, they are going after sailing pretty early (I would think) to get that dangerous UB out. Which unfortunately spirals off into yet another +1 for navigation bonus when they circumvent the world.
I would be more inclind to get sailing just so that we can sink their scout-boat(s) and galleys if they try to sail past us so we can block it. Of all the players on this map, the LAST person on earth we want getting the circumnav bonus is Ragnar. That's too dangerous for us (and everyone else).
If things go well for us here, we will be the first to triremes, and possibly by quite a large margin. We can even take liberties early and go on the offensive, pillaging sea tiles and there isn't a damn thing anyone can do about it. Unless they whip a big stack of galleys, which is going to be impossible since we are pillaging their food to begin with, haha!
But come what may, our diplo team needs to try to let the other teams all know that Ragnar is the danger on this map many times over. I think the Amazons on the other hand are crying. They may be realizing now that their Imp rush isn't going to work unless they get a bunch of galleys, and even then it isn't going to work. WE SHALL SEE!