If you or anybody else still have this problem, this might fix it:
- go to town edit
- first use testingcheatsenabled, then EnableLotLocking true
- click on the dive spot and click on the little lock in the bottom right to unlock it, then go into build/buy mode
- go underwater and find the cave, then click it (so you're holding it) and place it back again (I couldn't actually place it back again because there is stuff in the way, but ctrl + z put it back)
- go out of build/buy and lock the lot again
- go out of town edit and save
This is something I have to do again everytime I start playing, but at least it's a temporary fix. All credit to someone on the internet whose website I sadly can't recall.
