A tidal wave.
Rather than focus on the laborious task of changing direction, it might very well be better to consider the absurd. If you can make a tidal wave, you can turn a lot of oil tankers. Of course, you need to figure out how not to sink them.
I was at a dinner party tonight with a bunch of people who, perhaps without knowing it, figured out how to make tidal waves. I suspect they did not focus on the specific problem of turning a single oil tanker. In fact, I think Niklas and Janus knew, once they had learned how to make tidal waves, they could do a lot more than turn ships. Thanks for a pleasant and illuminating evening.