You're welcome, I'm glad that was helpful and I imagine you aren't the only player looking for that info. Thanks!
Have you found the submarine? It has a distinct deepwater color palette and soundscape. There also are a few coral reef and lagoon study spots with music. They're a bit hard to find but if you walk along certain beaches and listen carefully you might hear some clues ;) You also might be able to see them from certain viewpoints.
We had begun to prototype a deep water minigame linking the island to the city, but we ran out of time. We wanted to get this out asap so that it could support students during the pandemic. I agree it would be fun to make and play though. We'll have to think over if we have capacity to create upgrades in the future. Right now we're both working on other projects ( I'm working with another team on https://www.kaiunearthed.com/)
best,
M