Title text:
They're up there with coral islands, lightning, and caterpillars turning into butterflies.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3135/
Huh. TIL that there are three common types of tidal cycles and which one you get depends on geography, location, ocean currents. https://beltoforion.de/en/tides/tidal_cycles.php
And yeah, dinural is apparently the most rare of the three. Wild.