We have seen a lot of different structures tied up with some ecofriendly intent but here is something interesting for you called the Sea Tree. Apparently the Sea Tree is something that would be perfect for creatures. Unfortunately, it is limited to animals and hence is not suited or made for humans.
This is a tiered structured moored underwater that will come with a cable that will serve as the frame for its series of layers. The whole thing is a concept by Waterstudio.nl. What makes the Sea Tree unique and interesting is that it that finds a way to create the structure for nature rather than retrofitting a green space into an urban structure or create a mixed use building.
The idea was meant offset the trend of city sprawl and could be located in any water source — lakes, rivers or oceans