I'm honestly not sure what the point of those hidden lots are? Like you can fish there and dig, and collect plants but you can do that anywhere? Plus as far as I know, there isn't anything directing you to these hidden lots. Maybe if they patched in an aspiration to accompany the secret lots players might know they exist or maybe give us a reason to visit them? As far as I'm aware those lots do everything a park can but they're more annoying to get to.
Plus a dive lot I don't think would have been considered a secret lot, it would be more considered what the movie studio (GF), hospital, and police station are... Maybe the could have treated it like an active career where you can choose to follow your sim under the water? If you were visiting to find mermaids then follow, or for special collectibles... or for mermaid kelp seashells, etc, but I still think with a closed world, not including a diving lot is a huge missed opportunity.
