Making marine reptiles and other marine animals able to exist in lakes (water bodies created by the player through the environment tool). Please implement this! It would make creating an ecosystem so much easier.
I wrote in multiple threads about the need of alterntive Soruondings for the Lagoons !
The one ( and sadly only) naturall Lagoon of the Malta DLC shows that at least rocky shores for the Lagoons ( or parts of them) would be possible !
For Side B isles or simply more natural looking enclosoures Rocky shores or sandbeaches would look sooo nice !
A way to do it would be having natural looking decorations be able to clip on the edges and cover most of the lagoon. Have rock formations surround the enclosure. And it would work well with the new rock island structure coming in the next PDLC.