Thats quite a piece. Kudos to your effort :) 

Yeah, that's why this projection was in use by engineers and architects before 3d-modeling became usual - it can be easily drawn on a paper with pencil, eraser and two wooden triangles.

 I love these kind of axonometric projections and it all comes back to the Last Ninja on the C64 for me.
What is useful is that they demand scale-relationship and is measurable + that one has somewhat different rules for shadows and reflections unlike the 1-3 point perspective.

weezllane technically they're poor but they look surprisingly cozy than the horizontal ones.

......

 the penguins are incredible!

Your shadows look really good. I can understand how they could have been a challenge. Nice work.

Lovely work! Usually, I do not like these Iso-Cities people do. But this one reminds me of Transport Tycoon.

Thanks for comment, Sergiotron. I tried texture water - it looked awful. I'm not yet so skilled. I only added cntours of 'underwater objects. As we can see here, transparent objects (including water) is issue where the color is probably everything. Also the problem can be that it's the same color as the ground - I tried to do it darker but with no success.

This looks very good :), but I think your sea needs texture. It took me a while to realise that was water.