It would be the same way it can track the phases of the moon. Assuming the watch knows where it is in the world (either by GPS or on older ones by you setting the location), the rest would just be a reference to tide charts. They change daily but so do moon phases. In fact, the two things are connected (moon and tide).
Ignorant question. How does the watch know what the tide levels are in your part of the world? Tide times change every day
It would be the same way it can track the phases of the moon. Assuming the watch knows where it is in the world (either by GPS or on older ones by you setting the location), the rest would just be a reference to tide charts. They change daily but so do moon phases. In fact, the two things are connected (moon and tide).