If you're looking for a more aquatic-based zoo game, give Megaquarium a try. It doesn't have as many animals as ZT2, with 90 marine species in the base game, and an additional 30 freshwater species in the Freshwater Frenzy DLC, but it does have an active modding community, just recently hitting 300 mods on the Steam Workshop. Currently the DLC and official mod support are only on the Steam version. Unfortunately it can be hard to build realistic exhibits, as building and decoration placement is grid-based, but mods help a lot in that regard. If that sounds good to you, here's the Steam page: Megaquarium on Steam