Yes, but in circumstances where no war is in the offing, digging a giant hole next to 50km of open water begs questions. It would be impossible to get "it's a hedge against the future" over the line.

The same to a lesser extent applies to pipes. You could construct pipes for gas, for some of the heavier oils and crude (what I read suggests pumping crude long distance is painful, it has to be down-mixed with lighter stuff to make it sufficiently fluid) but the fertilizer? that would mean converting dry to wet and back again (nobody ships fluid weight if they can avoid it) -Or ship the inputs: ammonia, and sulphur in some liquid form, and produce the dry goods on the other side.

But, I think pipes have a stronger case than a canal: move the things which are amenable to pipes, into pipes, and bury the pipes.

In times past, this would have been done as a convoy. China and other nations would have stepped to the fore, conducting safe passage with their own ships on the outside edge. But we're not in a world where this kind of thing works for anyone involved. Even offering to cover insurance risk doesn't look to have motivated ship owners to pass. (in times past, the US wouldn't have put itself or it's allies in this position, hence the reference to China)

Don't be fooled by mental images of what a convoy looks like: ships like these maintain massive separation. There's almost suction between hulls moving at this scale, if they were within 500m of each other there'd be chaos if one had to take any evasive action. In reality (I believe) even a convoy consists of a a lot of discrete, clearly demarked and targetable things, not a large mass you can "hide" in.

https://en.wikipedia.org/wiki/List_of_traffic_separation_sch... (and a lot of links off this)