There's no Moore's law for ship speeds. If there were, then in the century since tea clippers we'd have ships somehow zipping across the sea at a decent fraction of the speed of light, somehow using less power than the baseline.

In fact that probably would have already made the case for speed restrictions, as every multi-thousand-knot container ship created its own tsunami. There have long been speed restrictions on canals at a few miles an hour to avoid erosion.