I don't think I've ever gotten the islands to the pristine state, which is probably why I never saw this before. But in my current save, my sim went sunbathing at one of the beaches, I figure this is the only thing I'm likely to ever do in Sulani in this save, and cheated the islands to the final conservation stage. 2nd day of winter, I get this notice that it's baby turtle hatching season, and you can go to, um, the neighborhood with the volcano to see it. Took me a bit to find what I was supposed to be seeing, travel to the shipwreck lot for the shortest walk. I went to the vacant lot, my spellcaster sim just zapped himself right over but his very pregnant Muggle wife with low Fitness had a long swim. Looks like this is kind of a big deal in the islands, there was flags and stuff all set up, and a whole bunch of locals showed up to cheer the turtles on.