Ukraine doesn't have much of a merchant fleet. Most of their exports travel on foreign bottoms. And foreign ship owners are unwilling to risk entering an active conflict zone, especially because they can't obtain affordable insurance.

for a short while, while said aviation exists

we can play this game all day long, but the past 2 months have clearly shown that russian conventional forces are not even close to a match for NATO combined forces*

* as long as the goal isn't to slaughter as many civilians as possible, which for russia is a strong assumption