I just had a brain blast for what kind of animal could do this exhibit justice - sitatunga! A large body of water as well as a scenic set of islands, and San Diego (theoretically) has no shortage of hoofstock holding areas. Maybe some pelicans as well?
I don't think there's sufficient containment or infrastructure to support Sitatunga here - would need quite a bit of revamp work. The island itself is not tremendously large either.