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/
The mobile browsers I've used let you long-press the image to see the hover text.
If yours doesn't, you can always prepend
m.to the domain name, like this: https://m.xkcd.com/3090/Thanks for the tip!