Title text:
Turning in other directions can be accomplished by using a magnetized centerboard and ocean currents, since a current flowing through a magnetic field induces a Laplace force.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3090/
Regarding the edit:
The mobile link might be better than the usual link, but I'd still prefer the one-stop-shop of this current method. Comic, hover text, and comments are all viewable in one place without the additional wait of switching to a browser app and loading the page. I wish the desktop experience mimicked this.